[ADavis40]

Ok so I just bought my 1989 Ford mustang gt about 6 months ago, and when we bought the car it had a brand new 302 crate engine in the car. The previous owner said that the orginal engine had 252,000 miles on it and started smokeing so he replaced it with a new crate engine, we do not have recipts just taking the mans word which the engine looked great such as not oily or anything clean engine. So dad was talking to the man and he said that the new crate engine had 3,000 miles on it but when he first got it he put full synthetic oil in the car. Dad was not too happy about this he figured this could possibly hurt the engine because the rings could not seat in and could cause it too use some oil. So we have been keeping a close eye on the oil and it looks like the car is needing a quart of oil every 1,000 miles. The car does not smoke dad said that he saw it one day when we first started it up, it had a puff nothing major just a puff out of the right exhaust. So he is wandering could that man running synthetic oil cause the car using some oil and cause it to have a puff of smoke just that once? The cars runs great had too 132 mph runs great just don't know about the synthetic ordeal. Any info would be greatly appericated.

Thanks for all replies

[69fastback]

It's not likely that running synthetic hurt anything.

A puff of smoke on startup, but not smoking while running, is indicative of a a leaky valve seal. While the engine isn't running, oil will leak past the seal down onto the top of the valve. When you start it, it burns it and makes a puff of smoke.

[mustanginky]

ehh people go back and forth on the synthetic oil break in debate. here's my personal thought, conventional oils allow a motor to break in better. rings require a bit of friction to "wear" into the cylinder walls. synthetics may not allow it do to that. i broke mine in on conventional oil, and 500 miles later or so i have no oil upon start up.

also, break in procedure is as important as what oil is used. prime oiling system, let it run for a minute or two, drive it on a road with lots of stop and go, get it up in the rpm range with lower load. take it up a hill or two with a few 3/4 throttle runs up to 4-5k. just my .02c though.

[ADavis40]

Just wandering do you all think this engine is poorly rebuilt or what?

[69fastback]

You're just running in circles until a leak down check is done. That'll tell you everything you need to know.