changing from mineral to synthetic oil

AFAIK, virtually without exception, semi-synthetic is better than mineral and fully synthetic is better again.

Are there any issues though with changing from mineral to synthetic, particularly say if the car has been running on standard oil for up to 10 years? I had heard that a sudden change to synthetic with it's enhanced lubrication properties can cause carbon build-up and gunk to dislodge and clog up the engine.

Any truth in this?

If you're changing the oil and you think there's that much gunk, get the system flushed before you put in the nice expensive Mobil 1.

Also, note that 0w40 or 5w40 (as most semi-synth & fully synth oils seem to be available in) could make your engine louder. Tappets click more etc and mightn't sound as smooth.

For most cars that don't get driven hard, mineral oil would be fine...just don't buy yellow-pack oil. Decent mineral oil is better than cheap synthetic.

Pique318 said:

For most cars that don't get driven hard, mineral oil would be fine...just don't buy yellow-pack oil. Decent mineral oil is better than cheap synthetic.

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OK thanks...was thinking that apart from performance cars, the benefits of synthetic oil (when weighed against price) were maybe a bit overstated alright...

Go with original spec.

There really is not merit to changing a 10yr old car to fully synth oil. For a start, it's probably running on semi-synth already.

As for 'yellow pack oils' just remember, all oils are graded, and your car requires X grade, and there are relatively few suppliers of oil, but many colours of bottles.........in other words, a lot of it comes from the same place. E.g. 'BMW' oil, is made by Castrol. Except in the Castrol bottle it's cheaper than the one with the BMW badge on it.

Go by the specs, not the badge.

On a 10 yr old engine, there is also the possibility, however remote, that changing to a fully synth may prompt a few oil weeps, as seals and gaskets may react to a new oil composition. This is not unknown.

Oh, and the 'old' oil your car runs on, is cheaper - changing to new just means dumping a more expensive oil, at the same time intervals.....

RS2K said:

Go with original spec.

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i dont agree.
original spec will be probably the cheapest the manufacturers can source which is adequate to get the engine through its warranty period 100k miles or whatever.
a few years ago mobil ran a bmw 325i using "mobil 1 " on rollers for iirc something like a million miles , only stopping for servicing etc. when the engine was dismantled, all the twisty bits were still within tolerance for a brand new engine.