Its interesting to note that the majority of vehicle manufacturers
currently state (in their owner’s manual) a oil change frequency of
5,000 to 12,500 mile intervals. This is rather curious considering the
oil manufacturers only need to comply to a 4,000 mile interval to meet
the current API SL rating.

It should also be understood that the actual tests performed by the
API (American Petrouleum Institute) are numerous, but the 3 tests of
importance are the TFOUT (Thick Film Oxidation Uptake Test), the
Sequential IIIF test, and the test oil’s TBN (Total Base Number)
rating.

TFOUT measures an oil’s time to failure based on its oxygen absorbtion
rate, the Sequential IIIF tests the oil viscosty increase after 4,000
miles of continous subjection to heat, and the TBN rates that oil’s
level of reserve alkalinity.

Extending your oil change interval from 3,000 miles to 5,000 may seem
reasonable, but the truth is anyone that does this will only increase
the cost of vehicle ownership because the drop in your fuel economy
will far exceed the savings of changing oil less frequently. Extending
your oil change interval from 3,000 to 5,000 miles can result in as
much as a 20% drop in fuel mileage and considering the cost of
gasoline today this is nothing to ignore.

The vehicle manufacturers have increased their oil change mileage
intervals for no reason other than for the purpose of marketing their
cars and trucks. You need to look into what each manual states, as the
mileage interval listed is almost always stated for those vehicles
driven under their description of "Normal" driving. The general
description of "Normal" driving is those vehicles driven with a
single person, on a level surface at sea level, a steady state 55 mph,
and for trip lengths of no less than 50 miles at a time. If you drive
your vehicle outside any one of those previously stated conditions,
then you need to refer to the service intervals listed under
"Severe" driving conditions, which for Ford is 3,000 miles between
oil changes (the same is true for Chrysler, GM, Toyota, Honda, and
just about every one else).

Someone mentioned they ran their oil for 13,000 miles and had it
tested and it tested as good as new(?). I guarantee you that oil had
failed and was all but useless, as the lab he sent it into only tested
for contamination. The cost of performing a TFOUT, Sequential IIIF
test, and then measure an oil’s TBN would cost roughly $6,000 to
$7,000 to complete. (as an example, the Sequential IIIF test uses up a
GM 3.8L V-6 for each test)

Bottom line, change your oil every 3,000 to 4,000 miles or every 6
months, which ever comes first and only go beyond that mileage
interval if you’re using a high quality synthetic such as Mobil1 (even
then I would suggest you change your oil every 5,000 miles).

Bearracing