what weight would you recomend for a 152,000 mile 5.7L TPI
that gets driven hard and has mild valve seal leak i'm oil illiterate!
thnx

 

Highhat,

That would depend upon the temperature at which you are using the engine. At 40°F or above, I would suggest 10W30 for daily driving or 20W50 High Performance under high heat and load use (racing).

Between -20°F and 80°F, 10W30 but avoid heavy loads, like constant racing. With regular use below -20°F, you might want to consider 5W30.

That should satisfy the GM recommendations and protect your engine very well. The apparently higher viscosity numbers at low temperatures are a little misleading, since synthetics typically pump, flow, and lubricate at much lower temperatures than a mineral oil with the same viscosity rating numbers. 10W30 Mobil 1 synthetic will pump, flow, and lubricate adequately at -49°F, and 15W50 Mobil 1 pumps at -38°F. Try to find a mineral oil with that performance, and it won't have a 10W or 15W cold rating. It's a new game.

 

Thanx Vader, for the info I live in missouri so the temp varies greatly thru the seasons

 

I live in Texas and it will be plenty warm for a while. Can I use the case of 5W-30 Mobil 1 (that I have sitting around) in my 91 LB9 with 20,000 miles? What drawbacks would there be to doing this?

 

Personally, I'd save it for November and get the 15W50 for summer heat, but my engine is almost "worn out" at 47,000 by comparison. 20,000 in twelve years? Don't you ever let it sit, or do you just drive constantly? At that rate, it will be ready for the scrap heap in 80 years or so...

 

I would not put synthetic oil in an engine with 152k miles on it unless it was rebuilt sometime recently. You're likely to develop oil leaks.

 

I bought the car from a guy in Flint, Michigan. It was his "summer car." I found in on autotrader.com, called him, and flew up to get it. He had a REALLY nice house, land, other vehicles, and the car only had 15, 9xx miles on it (and no rust except for exhaust manifolds, surface rust on rear axle and such) so I don't doubt that he was telling the truth when he said that he stored it winters and only drove it sometimes in the summers.

Since I have been modding it when I haven't been studying for the past seven months, I've only put another 4,000 miles on it since I bought it last fall. It just may live to be 80 at this rate!

Thanks for the oil advice.

 

It shouldn't create leaks, only make ones there worse.

 

Mine has been wintered in a heated garage, under a dust cover, since I've owned it. I bought it from a guy down the street who owned it since it was new, and did the same thing (except for the heat in the garage). I'm sure I'm not the only one. I've only put 10K miles on it in the past eight years, and the use gets lower every year with other "toys" to play with. It's becoming the definition of a "garage queen".

As for the oil leakage, the newer formulation of Mobil 1 has seal conditioners that can combat the "dried seal leak" syndrome associated with earlier synthetic lubricants. If a leak was there but masked by sludge and varnish, it will appear larger with the synthetic. If it was caused by hardened old seals, it may eventually go away with the newer formulations of Mobil 1. It swells nitrile and EPDM rubber compounds pretty well.

Mark is all over it, though - they could initially get worse.