I have a 92 350TPI with 150,000 miles on it.What motor oil should I use in it and how many quarts?I know sounds dumb but I haven`t had the car long and I want to be right.Thanks

 

This is a very bad question to ask. It invariably starts a flame war among various partisans of one type of oil or another. Few things seem to bring out as much ignorance and repetition of McDonald's parking-lot hearsay and the like, as well as blind loyalty or hatred to particular brands. It's alot like the cigarette mfrs; people can't tell you in a blind test what brand somebody handed them, but they are fanatically loyal to the one that they prefer. It's all in their heads.

Personally, I recommend new, clean, fresh oil as the best kind. Fill it until it reaches the "Full" mark on the dipstick, and no more. It will take between 4½ and 5 quarts depending on what filter you use.

I'd suggest sticking with the factory viscosity recommendation, 10W-30. There is no need for anything thicker, or special additives or formulations, or any of the rest of those folk tales that will surely get posted, and which of course will bring on the arguments.

I prefer synthetic such as Mobil 1. Others may prefer Valvoline, Castrol, Amsoil, etc. etc. etc. Any of them are better than old worn-out contaminated oil.

 

sofakingdom has a few points that i agree with and dont.the first thing is oil quality. there are many different brands and of coarse people have there prefrences mine are valvoline, royal purple, redline and ams oil. For your everyday driver i would recomend a standard oil. STAY AWAY FROM SYNTHETIC ON AN ENGINE WITH THAT KIND OF MILEAGE. You do not want put synthetic oil in an engine with that kind of mileage because synthetic has a way of helping oil seals leak that were not leaking before.SYN is great for young engines that do not have old and dry seals. It looks like you are in a relativley humid place so it might not effect you as much. With a motor with 150k i would be inclined to put a 10-40 oil it.
A general rule is the more loose a motor is the thicker the oil should be. Keep in mind that if you have worn bearings the thickest oil will not help. good luck.

 

5W30 or 10W30 depending on were you live. Change it every three months or 3000 miles and you can not go wrong.

 

Yes, an engine with that kind of mileage doesn't deserve to live.

Old, and no longer true, story.

 

You should run either 5w30 or 10w30 oil, around 5.5 quarts of it. I'd recommend a full synthetic such as Mobil 1.
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If the engine has the stock oil pan and you use the correct filter it takes 5 quarts. I personally like Royal Purle or Valvoline, Castrol and Mobil 1 are also good oils. I use the purple stuff in my Firebird, and Valvoline MaxLife 20W50 in my wife's 351 Cleveland powered Mercury Montego.

As far as synthetic oil causing problems in an old engine....I have not traditionally been a believer of that myself, but I started using Royal Purple in my old S-10 Blazer (at just over 150K miles) and some new oil leaks started and existing ones got considerabley worse. This all happened over the course of the last year to year and a half that I owned it. The previous 3 years that I used synthetic blend or conventional oil only it's oil consumption and seepage was constant. Coincidence? Yeah, it's possible. But that definitely put some doubt in my mind. Don't take that as concrete evidence though.

 

Before I started rebuilding my motor it had 145k. I used Valvoline High Mileage synthetic. Its supposed to do the same things as the normal high mileage oil, helping with old seals etc. but with the other benefits in synthetic. In the 6,000 miles I used it (two oil changes). My engine ran smoother and had better gas mileage. And most importantly it didnt leak oil like many people say. Now we all know there are different types of ways you can drive a car and rack up miles. You can take a car drive it hard and put it away wet and neglect the oil changes, or you can respect the car and do regular tune ups, oil changes and generally dont go WOT after every red light. In my case the engine was well maintained, and had been mostly driven conservatively and on the highway. So you cant say as a rule that you should stay away from synthetic in high mileage cars. Like all the different varieties of oils there are equally as many ways a car ages. Example a friend of mine had a 90' IROC that had only 90k. But it smoked on startup, used alot of oil, and lost alot of compression. Because of the way the original owner drove it, hard fast, all the time, and never did anything to it, oil, plugs etc.
So I think the whole conception that you only use synthetic in new engines is BS, although yes I believe that if synthetic oil was going to leak it would be in a higher mileage engine, but I wouldnt go as far to say that all would. It all depends on the condition of the motor.