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Car Forum / MINI / July 2003Use of unleaded petrol
I came across something interesting: In every source I have seen so far, it says that unleaded petrol can be used in Minis made after 1989, or in minis with hardened valve seats. I found a list of engine serial numbers that are compatible with unleaded petrol, but my engine serial number looks nothing like the serial numbers in that list (perhaps I am looking in the wrong place - The model in question is a 1988 Austin Mini City 998 Automatic) However - and this is the interesting bit - it says on the back of the Mini manual that came with the car that it drives on unleaded petrol, so I decided to give it a go. I have been driving on unleaded without lead replacement additive for a few weeks, and I can't say I notice any difference. Is my mini a freak occurrence of an 1988 car that drives fine on unleaded petrol, or were the sources I found on the net inaccurate? HJ > I came across something interesting: > In every source I have seen so far, it says that unleaded petrol can > be used in Minis made after 1989, or in minis with hardened valve > seats. Yep. This is because lead in petrol not only improved octane, it also helped lubricate vlave seats and prevent them wearing. > I found a list of engine serial numbers that are compatible with > unleaded petrol, but my engine serial number looks nothing like the > serial numbers in that list (perhaps I am looking in the wrong place As you say, you may be looking in the wrong place. Find the join line between the head and the block, underneath the spark plugs. Follow it to the radiator end of the motor, where a small section of the block "flares" out from under the head and bears the engine number. In Australia the number is always stamped into this land, but in the UK engine numbers on a rivetted plate are common. > - The model in question is a 1988 Austin Mini City 998 Automatic) Automatic engine numbers are slightly different, to indicate that the motor is an auto (they're different....) > However - and this is the interesting bit - it says on the back of > the Mini manual that came with the car that it drives on unleaded > petrol, As long as you're confident the manual belongs to that car and hasn't been borrowed from a different car.... > so I decided to give it a go. I have been driving on unleaded > without lead replacement additive for a few weeks, and I can't say > I notice any difference. You won't notice any difference for quite a while even if there is a problem. Valve seat recession is quite a slow process, and you can get away with the occasional tank of unleaded if you get stuck even with an older motor. It will drive just fine even as the valves wear the seats. > Is my mini a freak occurrence of an 1988 car that drives fine on > unleaded petrol, or were the sources I found on the net inaccurate? The fact that the car drives fine on unleaded means absolutely nothing and is no guide whatsoever to whether it can be run on unleaded long term. In fact this is the biggest problem - damage from unleaded is insidious, you don't know about it until it's happened. Graham. > > I found a list of engine serial numbers that are compatible with > > unleaded petrol, but my engine serial number looks nothing like the [quoted text clipped - 6 lines] > Australia the number is always stamped into this land, but in the UK > engine numbers on a rivetted plate are common. It may also be a reconditioned engine from someone other than Rover. Many reconditioners will use their own numbering.  SignatureRgds Steve steve@dsnclassics.co.uk www.dsnclassics.co.uk > > > I found a list of engine serial numbers that are compatible with > > > unleaded petrol, but my engine serial number looks nothing like the [quoted text clipped - 9 lines] > It may also be a reconditioned engine from someone other than Rover. Many > reconditioners will use their own numbering. Well it may say unleaded on the handbook, but if your Mini is indeed of 1988 vintage, I'd say the manual is intended for a later model. Have a look on the inside front page near the bottom, there's usually a printing date there. Trouble is your Mini may well appear to run happily on unleaded even if it doesn't have hardened valve inserts, but eventually (or sooner if it gets heavy motorway use) the engine is going to suffer. I know a lot of Mini folk use Shell Optimax petrol (unleaded too) as this has a higher octane the same as old 4 star, but you still need to use an additive. Taffy > Is my mini a freak occurrence of an 1988 car that drives fine on unleaded > petrol, or were the sources I found on the net inaccurate? > > HJ I was speaking to a generally respected mini specialist here in Perth who insists that running minis on unleaded is fine even without hardened seats or lead-replacement fuel additives. He said he has rebuilt 'countless' mini engines over the last several years and has not done anything to unleaded-proof them and hasn't had a single one back with problems from using unleaded fuel We've been doing this in North America for about 20 years. As long as you make adjustments for the lower octane rating it's not a big problem. Cheers, Kelley >> Is my mini a freak occurrence of an 1988 car that drives fine on unleaded >> petrol, or were the sources I found on the net inaccurate? [quoted text clipped - 7 lines] >unleaded-proof them and hasn't had a single one back with problems from >using unleaded fuel > We've been doing this in North America for about 20 years. As long as > you make adjustments for the lower octane rating it's not a big [quoted text clipped - 15 lines] > >unleaded-proof them and hasn't had a single one back with problems from > >using unleaded fuel The A-Series engine is particularly prone to valve seat recession, this is why it was the chosen engine when MIRA were testing lead substitutes. I have used minis without hardened valve seats on unleaded with seemingly no problems, but only if it was an old hack. I certainly wouldn't do it with an engine that I'd spent money on or cared about its life expectancy. |
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