Engine 94 GT oil

jozsefsz said:

This question often spawns a religious battle. From my own experience tearing down and rebuilding engines (I do this only as a hobby so that's about a dozen engines over 30 years - not hundreds or thousands) those where I've used a full synthetic, even if I really stretched the change intervals because I was cheap or lazy or didn't care about the car, had significantly fewer signs of wear as judged by the wear-ridges at the top of the cylinders and by the longevity of the engine before oil burning and compression loss occurred. In fact, I've had to send rusted out piles of junk to the scrapyard before the engine ever experienced failure. I've personally never had an engine where I used a full synthetic actually wear out before the rest of the car (like the transmission and body) wore out around it. This includes an 80's Ford Escort with 1.8L that went for 250k miles and went to the junkyard with a good running engine. I had an '84 T-Bird with 5.0L where I changed the conventional oil religiously every 3k start to give out by 150k.

Full synthetic absolutely, whatever weight makes sense for your climate based on the owner's manual (with only 52k miles that's still a baby). I often use Mobil 1. Amsoil is really good stuff. Almost any of the full-synth on sale at your local autoparts store will be fine. Avoid the budget brands like the Walmart store brand as they've tested not-so-good. Use a good quality filter like Amsoil, Mobil 1, or even STP Extended Performance. Avoid Fram like the sad joke that it is. You don't need to use a high-zinc oil like flat-tappet cam engines require (or zinc additives) as the roller-cam is good without. I change mine every 5-10k depending on how much I care about the car and how much I beat on it. My '95 turbo gets it changed annually regardless of mileage (which is often just 2-3k) because of the extreme heat that applies to the oil.

Some folks say you'll get leaks from old gaskets / seals if you switch a car that's always used conventional to synthetic. I've never had that experience. I imagine it could happen, but personally I'd rather change a gasket than an engine if it did happen, and it would indicate to me that seal probably wasn't far away from failure anyways.

I'm sure there are lot of good opinions to be shared. The one I avoid is 'any API rated oil is fine, conventional or full-synth, just change it regularly.' That's not at all true in my experience.

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