Help with oil choice (Penn 10w40, 15w40, or M1 15w50

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Jun 19, 2002
Well, it's coming about time to change my oil in my old Corvette. When I noticed the price of M1 SS went down from $4.78 to $3.78 per qt, I decided that was what I was going to run. But I'm having second thoughts. My engine was rebuilt about 12k mi ago (since Nov) and I did not ask or get the clearances, but I believe it to be a bit loose. With the current 10w40 oil, I see 20psi hot idle (800 RPM) oil pressure. I do not want to chance it with a xw30 oil in this engine, but I don't really want to run the 15w50 M1 either (and am too cheap to pay $5 for the 0w40 M1). I have an 8 qt (with filter) oil capacity. I was thinking of running the Pennzoil 15w40. The car does not have cats. It's on the high side of the 40 weight which is good, but with the colder weather coming up, I looked down the aisle and saw an 8 pack of regular Pennzoil for $9.44 ($1.18 per qt!). Now, I'm thinking of running regular Pennzoil 10w40 during the winter (vis 118/12.5 @40C/100C) and 15w40 (vis 88/13.5 @ 40C/100C) during the summer months. I may also consider using a little AutoRx in each change to keep things clean. What do you think? I've been a syn user for too many years now to cross back, but I think the SL dino oil may just be a better bang for the buck.
Well, driving home from work, I think I convinced myself to go with M1. I figure the yearly difference will be about $100 ($150 if i go with 0w40). I'll probably end up mixing 15w50 with 10w30 in the winter and straight 15w50 in the summer. It almost never gets below 30F here and according to the Mobil1 temp vs vis chart, the 0w30 vis at 0F is the same as the 15w50 vis at 22F. So, even if I don't mix it, I should be safe.
Comp Cams solid roller XR274 236/242 @ .050 with lift somewhere near .560/.580 (I don't remember exactly). The springs are around 160/470 closed/open. I'm currently running Royal Purple 10w40, but was using Havoline first and then Pennzoil. None of the dino oil stayed in for more than 1500 miles. The RP has been in for 2700 miles and comes out at 3k.
Just mix the 10W-30 and the 15W-50. I've done it for a couple of years. I have been using 1 qt of the 50wt and 3 quarts of the 30wt. You could perhaps go 50/50. Snce neither has any VI (probably) the resulting mixture should be pretty close to a 40 wt. at 100C. I'm sure others will correct me I am out in left field. [Eek!]
Originally posted by sprintman: ChrisA Why not Delvac 1 5W40?? M1 on steroids as they say. Better additive package etc.
It's a lot more costly though, and it sounds like he's trying to keep costs reasonable. Which begs the question, why not go with Schaeffer 15w40? It's priced lower than M1 and has great cold weather performance for a 40wt oil.
ChrisA, I don't think any of your choices are bad. For a typical muscle-car (pushrod V8) rebuild, I'd go with a 15W40 with a good additive package and change it fairly frequently (3,000-4,000 miles). My choices would be the following (in order): 1) Schaeffer Supreme 7000 2) Pennzoil 15W40 Long Life 3) Chevron Delo 400 I would NOT, however, use auto-rx with each oil change. Unnecessary in a fresh motor and who knows what prolonged use of those compounds may do to your seals. Even if it's a small risk, I'd rather just changed the oil and filter 1,000-1,500 miles early if you're that concerned with cleanliness. If you really want to use the best synthetic, then I'd go with Red Line and eat the price difference. [Wink] --- Bror Jace
I may go with the Delvac 1 if I could find it at a decent price here. None of the Wal Mart stores I've been to carry it. I also have a hard time spending over $4 per qt for oil. Schaeffer would be a good option, but I don't want to mail order my oil. Also, from what I've heard, after shipping (and tax if I buy through Tim) I don't think it is less than M1. I havn't ruled it out, but at this time I'm still going OTC.
Chris,the lobe intensity of the intake is 38 which is in the racing category,50 or so in still a fast ramp and even 60 is a good performace cam but that Hydraulic roller lifter I do not believe will like the 15/40 HD Dino oils Summer or especially winter. You need a thinner VI oil with exellent boundry protection imo It appears you have .002 rod and main clearance,just guessing by the oil pressure and synthetic multi vis used Good luck on your decision,if you want a couple alternatives,email me
Chris, I'd run the Mobil 1, 15w-50 for eight months out of the year and run the M1, 0w-40 in the winter. Again, I like to keep oil pressure in the 15-20 psi/1000 rpm range for a street application, so you can use that as a general guideline.... TooSlick
dragboat, It is solid, not hydrolic lifters. I'm not sure that makes much difference, but figured I'd point it out anyway. I'll take it to email if that is what you want.
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