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Car Forum / Saab Cars / May 2006Regular gas in a 9.5?
I recently purchased a '02 9.5 Linear with 80K on it. I'm friends with the previous owner and know for a fact that she's never put anything but regular (87 octane) gas in it and experienced no performance problems save one time when it surged momentarily in 5th gear (it's a standard). In the two weeks that I've had the car, the surging, or hiccupping, or whatever you might call it has come on strong. It's always had regular maintenance, oil changes every 3K, and I just changed the oil myself last week. I know - now that I looked at the damned thing! - that the book says to use at least 90 octane gas, which I will if I absolutely have to, but does the condition described above sound like it was caused, all of a sudden, by improper gas usage? I just put my first tank of 89 octane gas - hoping for the best - in this morning and see no changes. Yet. Opine, please. Michael > the book says to use at least 90 octane gas, > which I will if I absolutely have to Why so reluctant ? It's not a farm vehicle ! Graham > the book says to use at least 90 octane gas, > > I just put my first tank of 89 octane gas - hoping for the best - Why still not even 90 octane ? The advice is *at least* 90 octane ! " Occasionally you get some genius who takes the opposite tack--he spends an extra 10 or 20 grand buying a high-performance car, then decides he's going to save three bucks per tankful using regular instead of premium as specified. He figures as long as the engine doesn't knock he's OK. Wrong, carbon monoxide brain. Car engines nowadays contain knock sensors that detect detonation and automatically retard the spark to compensate. The delay means maximum gas expansion occurs when the piston is farther along in its downstroke and thus there's more room in the cylinder head. This reduces peak cylinder pressure, eliminating knock but also giving you less power and poorer mileage. " http://www.straightdope.com/columns/041008.html Graham > > the book says to use at least 90 octane gas, > > [quoted text clipped - 15 lines] > > Graham I appreciate the 'straightdope,' Graham. I'm not trying to be cheap; I'm just trying to avoid the shedding of any shekels that I might otherwise have and hold, for better or for worse. What Fred said below, re: the 87 v. 89 v. 90 situation, seems to make sense to me. On the other hand, what I don't know about cars and engines is staggering, even to me. The Straightdope article was a help, and I need all of that that I can wrangle. Cheers, M > I recently purchased a '02 9.5 Linear with 80K on it. I'm friends with > the previous owner and know for a fact that she's never put anything [quoted text clipped - 13 lines] > > Michael To resolve your problem, which is definitely not related to the grade of gasoline you are using, try swapping in some new spark plugs. Don't use anything except the proper NGK plain jane plugs called for in the owners manual. From there on out, you should probably use 89 octane in a linear. There is no such thing as "90" octane in the US. It is 87 (regular), 89 (mid-grade) and 91 to 93 (super/premium) depending on location. The small difference between the gas certified to be 89 (or better) and 90 is pretty insignificant. If you wanted to be anal about it you could squirt in a few gallons of premium fuel every tankful of mid-grade, but since the mid grade is at least 89 (most likely somewhat more) it is not a very big deal. OTOH, running the lowest grade as the PO did is not so great as it will cause the ECU to run with a retarded ignition timing pretty much all the time. You won't get the best mileage or best performance that way.  Signature-Fred W > > I recently purchased a '02 9.5 Linear with 80K on it. I'm friends with > > the previous owner and know for a fact that she's never put anything [quoted text clipped - 21 lines] > From there on out, you should probably use 89 octane in a linear. > There is no such thing as "90" octane in the US SPUTTER! > -- > -Fred W Thanks, Fred. What you say makes sense. I'll give the spark plug swap a go - couldn't hurt, surely - and continue with the 89 octane. FWIW, on this morning's 35 mile commute, I noticed none of the problems that I bitched about earlier. Cheers, M > Thanks, Fred. What you say makes sense. I'll give the spark plug swap a > go - couldn't hurt, surely - and continue with the 89 octane. [quoted text clipped - 4 lines] > > M You're welcome. By the way, do you work at Red Dot? Just curious based on your email addy. If so, I'm located just east of you a-ways in southern NH (Manchester area). Signature-Fred W > > Thanks, Fred. What you say makes sense. I'll give the spark plug swap a > > go - couldn't hurt, surely - and continue with the 89 octane. [quoted text clipped - 13 lines] > -- > -Fred W Yup. Red Dot, in Bondville, VT. Just shy of Manchester, VT. M >>>Thanks, Fred. What you say makes sense. I'll give the spark plug swap a >>>go - couldn't hurt, surely - and continue with the 89 octane. [quoted text clipped - 17 lines] > > M Cool Beans... and where, pray tell, is your domacile (35 miles away)? What a great gig that must be though, living large in the Green Mountains... Signature-Fred W > From there on out, you should probably use 89 octane in a linear. > There is no such thing as "90" octane in the US. It is 87 (regular), 89 [quoted text clipped - 4 lines] > since the mid grade is at least 89 (most likely somewhat more) it is not > a very big deal. Interesting, ain't it, our petrols over here are all unleaded and are 91, 96 and 98 octanes. My 9000 Aero likes 98 as recommended, but this is not available everywhere, so it usually runs happily on 96. SignatureRichard Sutherland-Smith Wanganui 5001, NZ >> From there on out, you should probably use 89 octane in a linear. >>There is no such thing as "90" octane in the US. It is 87 (regular), 89 [quoted text clipped - 8 lines] > 91, 96 and 98 octanes. My 9000 Aero likes 98 as recommended, but this > is not available everywhere, so it usually runs happily on 96. Ricky, Your talking RON, and we rebel yanks are talking PON (Pump Octane Numbers) which is RON+MON/2. So your 96 is our 89. But I'm not entirely sure of the happiness of my SAAB's engine either way... What is perhaps of interest (and maybe this was the point of you post) is that the bigger gap is between your "low grade" and your mid-grade. Why anyone would pay a big premium for 2 points of octane is a reasonable question. Here, the smaller gap which is between the low and mid grades (87 - 89) costs about 10 cents per gallon, and for another 10 centavos you get the big jump to 93 (4 points more) Signature-Fred W > >> From there on out, you should probably use 89 octane in a linear. > >>There is no such thing as "90" octane in the US. It is 87 (regular), 89 [quoted text clipped - 19 lines] > Why anyone would pay a big premium for 2 points of octane is a > reasonable question. In the UK many places only sell 95 RON ( e.g. supermarkets ) with an alternative 'superunleaded' being 97-98. 95 is fine for most cars but some perfromance vehicles get some extra performance from 97/98. I'm puzzled by your suggestion that 96RON = 89PON. This table suggest more like 92PON. http://www.btinternet.com/~madmole/Reference/RONMONPON.html That also makes 95RON ( which I normally buy ) equal to 91PON which makes sense to me for use in a Saab. Graham >>>>From there on out, you should probably use 89 octane in a linear. >>>>There is no such thing as "90" octane in the US. It is 87 (regular), 89 [quoted text clipped - 34 lines] > > Graham Right you are... 96 RON should be about the same as 91 PON (aka AKI) Signature-Fred W But the bottom line going back to the earlier post that some folks are missing the point of. You can use lower octane gas but you will get less power per gallon/liter and you will need to push on the pedal more for the same output. More gas per mile, less mpg. As gas prices rise (at least in the USA) the actual per gallon difference between 87, 89, and 93 octane seems to remain the same. That means that on a percentage basis, the cost of using premium is on a steady decline. Since the percentage difference in mileage is not changing, the cost and advantage of using higher octane gas is increasing. Whether or not it makes sense to use premium for your driving style and conditions is something you need to test over multiple tank fills. > But the bottom line going back to the earlier post that some folks are > missing the point of. You can use lower octane gas but you will get > less power per gallon/liter and you will need to push on the pedal > more for the same output. More gas per mile, less mpg. Not necesarily. The energy contained in the fuel is the same. If the engine computer (ECU) retards the timing it is because the fuel is burning too fast (pinging) and the combustion is happening before TDC. If the ECU does a correct job of backing off the timing is could have no effect on mileage. Taken to the other extreme, if the engine was set-up to run low octane (fast burning) fuel and you fed it very high octane (slow burning) fuel it is possible to have incomplete combustion and be exhausting unburnt fuel. Obviously that would nbe counterproductive to fuel economy. > As gas prices rise (at least in the USA) the actual per gallon > difference between 87, 89, and 93 octane seems to remain the same. [quoted text clipped - 4 lines] > driving style and conditions is something you need to test over > multiple tank fills. I agree with all of the above except the assumption of *better* fuel economy when running higher octane. The try both and see is the best approach. Signature-Fred W >Not necesarily. The energy contained in the fuel is the same. If the >engine computer (ECU) retards the timing it is because the fuel is >burning too fast (pinging) and the combustion is happening before TDC. >If the ECU does a correct job of backing off the timing is could have no >effect on mileage. Backing off the timing is going to seriously reduce power on a practical basis. >>Not necesarily. The energy contained in the fuel is the same. If the >>engine computer (ECU) retards the timing it is because the fuel is [quoted text clipped - 4 lines] > Backing off the timing is going to seriously reduce power on a > practical basis. Normally I would agree with you, that is if the fule octane was held constant. In other words, if the fuel burns at a constant rate (octane) then retarding the ignition would cause the fuel to not have enough time to complete combustion and you would lose energy. But if the reason the ignition is that the engine is pinging due to early combustion of the fast burning, low octane fuel, doesn't it make sense that the fuel will still be fully burned during the power stroke? Signature-Fred W >But if the reason the ignition is that the engine is pinging due to >early combustion of the fast burning, low octane fuel, doesn't it make >sense that the fuel will still be fully burned during the power stroke? I'm certainly not an engineer - but my crude understanding is that we advance the timing to start the burn earlier in the stroke and gain more power, but that it requires higher octane in order to do this. If I am not misunderstanding your statement, it seems like you are inferring that we advance the timing to compensate for higher octane gas and that therefore we get the same power from lower octane and retarded timing. If that was true, there would be no reason to have higher octane gas - we'd just retard the timing on all cars. >>But if the reason the ignition is that the engine is pinging due to >>early combustion of the fast burning, low octane fuel, doesn't it make [quoted text clipped - 9 lines] > retarded timing. If that was true, there would be no reason to have > higher octane gas - we'd just retard the timing on all cars. What you say makes a great deal of sense. I think the idea is that we want the majority of combustion to be occurring during the optimum part of the power stroke so that the angle of the crankshaft is as close to perpendicular to the cylinder as possible for best energy transfer from reciprocal to rotational. Obviously, it is not a binary situation. There is a ramp up and ramp down of the combustion and the expansion of gasses. To achieve this optimum angle at higher engine rpms requires igniting the mixture before the piston reaches TDC (advance). But with low octane fuel the mixture burns too rapidly and starts to expand before the piston reaches the top, causing pinging (preignition). The ECU retarding the ignition can reduce the preigintion, but that will not necesarily put the maximum combustion at the optimum crank angle. And then there is the whole valve timing thing... The other thing that does happen with low octane fuel is spontaneous combustion if/when the combustion chamber pressure and temperature are high. Higher compression engines make more power than lower compression ones (all other things being equal) and so the need for higher octane fuel. Boosting the intake pressure (supercharging or turbo charging) is the functional equivelent of increased compression (and increased displacement) and so requires higher octane fuels. Signature-Fred W > > >> From there on out, you should probably use 89 octane in a linear. > > >>There is no such thing as "90" octane in the US. It is 87 (regular), 89 [quoted text clipped - 25 lines] > 95 is fine for most cars but some perfromance vehicles get some extra > performance from 97/98. My 9000 2.0 LPT also runs better on Shell Optimax 97 or 98? Less likely to stall at full acceleration. These premium fuels also have cleaning agents which are beneficial. >>>>>From there on out, you should probably use 89 octane in a linear. >>>>>There is no such thing as "90" octane in the US. It is 87 (regular), 89 [quoted text clipped - 29 lines] > to stall at full acceleration. These premium fuels also have cleaning > agents which are beneficial. Can't say about your fuel market, but the gasoline in the US claim to have the same cleaning agents (detergents) these days regardless of grade. Of course each manufacturer claims to have the best compared to the competition, but do not differenciate premium anymore. I have not heard those claims of superior cleaning agents in "premium" fuels in over a decade. Back in the 60's and 70's it used to be a big marketing point... Signature-Fred W > >>>>>From there on out, you should probably use 89 octane in a linear. > >>>>>There is no such thing as "90" octane in the US. It is 87 (regular), 89 [quoted text clipped - 38 lines] > fuels in over a decade. Back in the 60's and 70's it used to be a big > marketing point... In the late 80s here Shell advertised its petrol as having superior additives. Unfortunately they didn't agree with all engines and some ended up with fouled valves IIRC ! Graham >> I have not heard those claims of superior cleaning agents in "premium" >> fuels in over a decade. Back in the 60's and 70's it used to be a big [quoted text clipped - 3 lines] >Unfortunately they didn't agree with all engines and some ended up with fouled >valves IIRC ! The gas/oil companies lost a major suit brought by the US gov't just a couple years ago for claiming that higher octane fuels had any benefit at all aside from higher octane. They use the same additives in high octane fuel, it just has higher octane. > >> I have not heard those claims of superior cleaning agents in "premium" > >> fuels in over a decade. Back in the 60's and 70's it used to be a big [quoted text clipped - 8 lines] > at all aside from higher octane. They use the same additives in high > octane fuel, it just has higher octane. OK, there goes my theory then... I'm not an expert, but a while back I remember that someone else had similar problems with a Saab at similar mileage, and I thought that it was a sign that the DI Casette was starting to fail? Can the repair-shop test this part to see if it's a problem, or is it a "I dunno, you could always replace it with a new one" kind of thing? I bring this up, because when my casette went on my 9-3 at 84K or nearabouts, the car suddenly lost power while I was driving on a highway, and that was not a completely pleasant experience. And apparently, this is a known issue with Saab electronics (which Canada's "Lemon Aid" series of car guides has been slamming Saab for, for years). Can an expert comment on this issue, to make sure we get the straight dope, please? Fred? Thanks! -- Viktor > I'm not an expert, but a while back I remember that someone else had > similar problems with a Saab at similar mileage, and I thought that it [quoted text clipped - 16 lines] > -- > Viktor Yes, I had considered the cassette as well. But when those fail they usually do, as yours did, suddenly and completely. My experience has been that as the sparkplugs age you get intermittent problems such as what the OP has experienced. The plugs are cheap and can be put in by almost anyone (just don't over-torque them and strip ot the aluminum head). The change should be immediate and clear. Signature-Fred W > > Can an expert comment on this issue, to make sure we get the straight > > dope, please? Fred? [quoted text clipped - 14 lines] > -- > -Fred W Fred- You interest me strangely... when you say "almost anyone," do you really mean that? While I'm not a complete moron with things mechanical I'd have to admit to being somewhat more than a partial moron. Forgive this question in light of my last statement and tell me, doesn't the replacement of plugs require purpose-built and expensive tools and wrenches and things? If so, perhaps the purchase of said tool(s) would be offset by what I'd pay to have the things switched out. Yes? No? Thanks, M > You interest me strangely... when you say "almost anyone," do you > really mean that? While I'm not a complete moron with things > mechanical I'd have to admit to being somewhat more than a partial > moron. It's 4 screws and one plug connector. It's the 4 button-head torx screws you can see on the top of the engine on the rectangular cover-looking thing covering the valley between the two cams, and the red connector on the right side as seen if you're standing where you have to be to be doing this. > Forgive this question in light of my last statement and tell > me, doesn't the replacement of plugs require purpose-built and > expensive tools and wrenches and things? Spark plug wrench, which is supplied with the car and should be under your trunk floor. > It's 4 screws and one plug connector. It's the 4 button-head torx > screws you can see on the top of the engine on the rectangular [quoted text clipped - 8 lines] > Spark plug wrench, which is supplied with the car and should be under > your trunk floor. No foolin'? That sounds eminently doable, if eminently is the word I want. But don't the tips of the plugs themselves need to calibrated one how or another (I've heard reference to "setting the gap") or are they factory set and good to go out of the box? I appreciate this. Now I just have to figure out what a cam is. Thanks, Michael >> It's 4 screws and one plug connector. It's the 4 button-head torx >> screws you can see on the top of the engine on the rectangular >> cover-looking thing covering the valley between the two cams, and the >> red connector on the right side as seen if you're standing where you >> have to be to be doing this. > No foolin'? That sounds eminently doable, if eminently is the word I > want. I believe that it probably is, unless you wanted a different word. > But don't the tips of the plugs themselves need to calibrated > one how or another (I've heard reference to "setting the gap") or are > they factory set and good to go out of the box? I haven't had to reset gap on spark plugs in years. But a spark plug gapping tool (with gage wires) can't be more than 5 bucks at your local NAPA or whatever. Buy the right NGK spark plugs as stated in your manual, _that_ is critical. Every NGK I've ever bought has been properly gapped out of the box. > I appreciate this. Now I just have to figure out what a cam is. Bumpy sticks that spin and make the valves go up and down. But that's not important right now. It's really a piece of cake. Undo those 4 screws (the torx screwdriver is probably also in the car's toolkit), undo the connector (there's a u-shaped slidy think holding it latched together, slide it out the only way it can go), and lift the DI cassette straight up away from the engine. Well, not "straight", at the same angle the engine is. Up & towards you maybe 10 degrees, you'll see what I mean when you get there. It takes a bit of force (just a bit) because you're disconnecting the spark plugs at the same time. Up & out, plugs right there. Make sure there's no crap around the plugs to fall in when you take 'em out, there probably won't be. If any of the used plugs have tips which look different than the others, post a description here. Should be coffee-with-cream colored maybe dusty looking. Black, or slimy, or flaky, or gone, would all be problems but I'd be surprised by any of that. > > No foolin'? That sounds eminently doable, if eminently is the word I > > want. > > I believe that it probably is, unless you wanted a different word. Excellent point. > If any of the used plugs have tips which look different than the others, > post a description here. Should be coffee-with-cream colored maybe > dusty looking. Black, or slimy, or flaky, or gone, would all be > problems but I'd be surprised by any of that. Thanks very kindly for the tutorial, Dave, and to Fred for giving me the plug heads-up to begin with. I'll be on those plugs like white on rice come this weekend, and may the automotive gods - Manny, Moe and Jack, as I recall - have mercy on my car's eternal soul. I will report back. M >> If any of the used plugs have tips which look different than the others, >> post a description here. Should be coffee-with-cream colored maybe >> dusty looking. Black, or slimy, or flaky, or gone, would all be >> problems but I'd be surprised by any of that. > Thanks very kindly for the tutorial, Dave, and to Fred for giving me > the plug heads-up to begin with. I'll be on those plugs like white on > rice come this weekend, Sorry, Swedish car, I believe you'll be meaning "like brown on a m00se". > and may the automotive gods - Manny, Moe and > Jack, as I recall - have mercy on my car's eternal soul. > I will report back. Try not to drop anything into the engine while you have the plugs out. That would be double-plus-ungood. Um, sorry about this, but regarding that "under trunk" spark plug wrench, I just had a look under the trunk flap. Lug wrench, check. Jack, check. Jack handle, check. Torx screwdriver, check. Spark plug wrench. Spark plug wrench? No apparent spark plug wrenches, and the Owner's Manual makes no reference to one. Either I'm looking in the wrong place, at the wrong thing, or it's been absconded with! M > Um, sorry about this, but regarding that "under trunk" spark plug > wrench, I just had a look under the trunk flap. Lug wrench, check. > Jack, check. Jack handle, check. Torx screwdriver, check. Spark plug > wrench. Spark plug wrench? No apparent spark plug wrenches, and the > Owner's Manual makes no reference to one. Either I'm looking in the > wrong place, at the wrong thing, or it's been absconded with! Should be a tubular steel device, plated in that gold-ish color like the lug wrench. Hole in the side of it that the lug wrench fits into as a handle. Maybe not? > > Um, sorry about this, but regarding that "under trunk" spark plug > > wrench, I just had a look under the trunk flap. Lug wrench, check. [quoted text clipped - 6 lines] > lug wrench. Hole in the side of it that the lug wrench fits into as a > handle. Maybe not? Not. But one shouldn't be too hard to come by, should it? Are there different sizes or depths or grades or anything, or can I just pop over to Bond Auto a grab a generic spark plug wrench off the shelf? > Not. But one shouldn't be too hard to come by, should it? Are there > different sizes or depths or grades or anything, or can I just pop over > to Bond Auto a grab a generic spark plug wrench off the shelf? There are at least 3 sizes of spark plug wrench. When you buy the plugs (did I mention several times to get the correct grade of NGK only?), take one along with you and get a wrench that fits. It needs to go deep. > > Not. But one shouldn't be too hard to come by, should it? Are there > > different sizes or depths or grades or anything, or can I just pop over [quoted text clipped - 4 lines] > take one along with you and get a wrench that fits. It needs to go > deep. Roger. NGK. Deep. And thanks again. And keep things out of the engine. Right. Tell me, why do I feel like I'm about to re-enact an early Bob Hope routine? And without Jayne Russell, to boot. Over. Out. M "Painless Potter" Hudson > Roger. NGK. Deep. And thanks again. And keep things out of the engine. > Right. Just so you know, you're overplanning this whole adventure. Not criticizing, I recognize it because I've done it. > Tell me, why do I feel like I'm about to re-enact an early Bob > Hope routine? And without Jayne Russell, to boot. Ah, Jayne Russell. Thanks for the mammories. > > Roger. NGK. Deep. And thanks again. And keep things out of the engine. > > Right. > > Just so you know, you're overplanning this whole adventure. Not > criticizing, I recognize it because I've done it. Overplanning? Nonsense! It's paranoia, a history of incompetence and deep seated feelings of inadequacy. Nothing more. > > Tell me, why do I feel like I'm about to re-enact an early Bob > > Hope routine? And without Jayne Russell, to boot. > > Ah, Jayne Russell. Thanks for the mammories. You're welcome. Now, pass me my head lamp and pith helmet, and let's get to work! M >> > Tell me, why do I feel like I'm about to re-enact an early Bob >> > Hope routine? And without Jayne Russell, to boot. [quoted text clipped - 3 lines] > You're welcome. Now, pass me my head lamp and pith helmet, and let's > get to work! Only if I get to be Bing, rather than Jayne. Wardrobe incompatibilities, you see. |
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