Let me second the notion for 10-30. The only reasons to run a thicker oil are low oil pressure (a loose tired old engine), to lessen oil consumption (once again a tired old engine), or for continuous high speed operation (and even then the need for 20-50 is debateable, 10-40 would probably be fine for hot high speed operation).
Many long years ago I worked the parts counter, I stocked straight 50w oil for the real oil burners.
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What is your oil pressure when hot at idle and at 3 grand? Almost always run 10 30 though, unless you need to bandaid a problem or run some high r's for a long time. This is just a generalization though....
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Well straight line from this counter jock is 10/30 for normal life, 10/40 for lots of highway driving and 20/50 for severe duty. As to the filter, I personaly think that Fram is junk. AC/Delco or the new K&N units which are basicly a beef'd out AC/Delco with a nut welded tot he bottem to aid in removal.
If you drive a lot in dusty or highly varied conditions, say rough country operation, then its recomended to change all your filters as much as you can and use fresh oil as often as possible.
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The bearing clearances have a lot to do with what weight oil you need. If you built the engine with about .0018 to .0022 clearance on the bearings then a very good quality 10W30 is all you should need. If you built it with around .003 clearance then you will need something thicker to keep your pressure up. The looser clearances will cause more oil to be thrown off of the crank and more oil consumption because of the extra oil on the cylinder walls. The thicker oil also takes more power to pump and puts more strain on the oil pump, distributor gear, cam and timing chain set. All this takes away power from the engine. It's my opinion that most performance engines should be built with .0018-.0022 bearing clearances and use 10W30. By the way, I like Amsoil synthetic oil and filters.
Very well said BBH. I personally have ran them all (the weights) with my old Suburban I have found she does run cooler with 10/30W, but she runs noisier than when I ran say straight 50w. She does have a lot of miles on her 185,000.
Just my .02
1989 Chevy Suburban/454tbi/2500/4x2/3:42;G80/F&R a-c/K&N air filter/180* Thermo Stat/10city;13 highway
Just so happens I visited the shop that built my 396 and asked the same question. He said the older engines require something heavier than the 10/30. He suggested straight 30 or better yet 20/50. He builds a lot of BBC's so I trust him. I use Kendall HP because it holds up better in high horse power engines that tend to run rich.
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