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Back round info: Located in Phoenix. "04 six speed coupe with the typical bolt ons. Calloway Honker intake, LG street pro headers, LG X pipe with high flow cats, SLP Power Flow/GTR axle back, street tune and Ron Davis radiator/180 T-stat and an Elite catch can. <24,000 on the clock.
Do not track or race, just trip drives and some spirited one offs. In the balmy summer months, when it is over 110, water temps 190-200, oil averages 205-215. I have been running Royal Purple 5W-30W HPS, six quarts with one quart Lucas synthetic stabilizer and a RP filter. Changed every spring, 3,000-3,500 miles. Oil pressure hovers around 25-30 PSI at idle, cruising around 40 PSI when at running temps.
Any feedback regarding the positives or negatives of switching to a 10-40 would be appreciated. Not interested in discussing brands of oil, just the differences a higher viscosity oil would provide.
Thank you in advance for any info provided.
Regards,
Chas
Stick to 5W-30. The bearing clearances were designed for this viscocity of oil and is why GM specifies this. Your oil pressure is exactly as it should be.
Going to a thicker oil can rob power and cause problems. Probably would be that big of a deal as it is not a huge jump in viscocity.
If you had your engine rebuilt and 10W-40 is what the builder specified, only then should you run 10W-40.
Stick to 5W-30. The bearing clearances were designed for this viscocity of oil and is why GM specifies this. Your oil pressure is exactly as it should be.
Going to a thicker oil can rob power and cause problems. Probably would be that big of a deal as it is not a huge jump in viscocity.
If you had your engine rebuilt and 10W-40 is what the builder specified, only then should you run 10W-40.
Space is correct. I have worked for 3 OEM engine manufacturers, and oil viscosity is directly tied to how the engine was designed. Use what is recommended.
2020 Corvette of the Year Finalist (performance mods)
C5 of Year Winner (performance mods) 2019
I agree with everyone above, use what is recommended for stock clearances especially with the low mileage on your engine since there likely isn't much wear anyway... as far as brand that is personal preference, just use something high quality and you should be good
Thanks to all that have posted replies. Being that I am going on 62 this July, I grew up with big block Mopar, Ford and GM engines. Remember running nothing but Castrol GTX 20-50 and sometimes straight 50W. I realize technology has changed but still cannot shake the heavier is better train of thought. We have an '07 classic chevy 1ton dually with an 8.1L big block that we pull a 12,000lb travel trailer with. 67,000 on the clock running rotella T6 with two oil filters. No problems at all and at times that motor whines out at the redline. Engine spec is 10-30, Rotella is 5-40. With the temps here in Phoenix being brutal in the summer, I always think that a heavier weight oil would be better. Maybe time to go back to school.
Again thank you for the positive and informative replies,
Chas
I wouldn't change at all, based on the pressures you're seeing.
If you wanted to go with 10W30, without the stabilizer, that might be an option to consider. Narrower ranges don't break down as quickly. But I wouldn't go 10W40 with that engine, unless as was mentioned, you get it rebuilt (new bearings throughout), in which case, talk with the engine builder about what oil is appropriate, or specify what oil you're using and have the builder build it specifically for that oil.
03 Z06 My LS 6 has 137,000 miles on it. this past summer had oil samples done before I had the heads ported an 102 FAST intake installed. Test results came back I been using 0W40 for the last 4 years an Mobil one filters. 7 years ago when I installed cam also HP oil pump, Oil pressure runs @ 50 PSI. I am not telling anybody they are wrong with remarks I can only go by my experience.
I run 0w40 because the bearing guru at Cummins (I was a design engineer for R&T) told me that is the best thing to do no matter what the car. It’s 2018 now and oils are a very different and advanced technology.
He said always run the highest and lowest viscosity you can get.
Just in case anyone doesn't realize this, the Mobil 1 5W30 that you buy today is nothing like the Mobil 1 5W30 that was available when these cars were in production and the owners manual was written and the oil cap was printed (and I'm sure that Mobil name got on the cap due to them giving GM a favorable oil supply agreement).
Just in case anyone doesn't realize this, the Mobil 1 5W30 that you buy today is nothing like the Mobil 1 5W30 that was available when these cars were in production and the owners manual was written and the oil cap was printed (and I'm sure that Mobil name got on the cap due to them giving GM a favorable oil supply agreement).
And?
Most guys act like because it's a Vette it's some kind of Voodoo to keep the engine happy. Guess what? That Vette engine is no different than the 5.3 in my truck that gets a synthetic oil change every 10,000 miles.
90% of the owners on this site never take their cars to redline on a regular basis.
The other 10 percent run the dog crap out of their cars on road courses, standing miles, roll racing etc. This 10% should study the oils they use, the 90% need to just cruise their cars, worry about what wax they use and follow the owners manual.
The point is to pick whatever oil you want to use. ANY top tier synthetic will work fine without the engine failing at just about any weight rating you chose. 5W30, 10W30, 5W40, 10W40 would all work with the car surviving past your ownership.
But, if you just "must" have the best for you car then the Euro blend 0W40 oils are pretty damn good and will work better than the new Mobil 1 5W30. I've been using Valvoline Euro 0W40 because it comes on sale about as cheap as any other full synthetic.
If you want to be technical then you need to follow the actual oil specification and not just the oil weight specified. Good luck matching that.
Last edited by lionelhutz; Jan 21, 2018 at 10:13 PM.
The bearing clearances in my forged 5.7L LS6 short block require a heavier weight oil, so I run 0w-40 on the street and will switch to either 5w-50 or 15w-50 for track day events.
Last edited by JHrinsin; Jan 24, 2018 at 02:01 PM.
This is the oil I use, good price and free shipping. My personal Blackstone Oil reports show it outperforms Mobil One. My car is a C5 Z06 and GM specifically requires Dexos and this oil has it.
Oil viscosity ?
Thanks to all that have posted replies. Being that I am going on 62 this July, I grew up with big block Mopar, Ford and GM engines. Remember running nothing but Castrol GTX 20-50 and sometimes straight 50W. I realize technology has changed but still cannot shake the heavier is better train of thought. We have an '07 classic chevy 1ton dually with an 8.1L big block that we pull a 12,000lb travel trailer with. 67,000 on the clock running rotella T6 with two oil filters. No problems at all and at times that motor whines out at the redline. Engine spec is 10-30, Rotella is 5-40. With the temps here in Phoenix being brutal in the summer, I always think that a heavier weight oil would be better. Maybe time to go back to school.
03 Z06 My LS 6 has 137,000 miles on it. this past summer had oil samples done before I had the heads ported an 102 FAST intake installed. Test results came back 
I been using 0W40 for the last 4 years an Mobil one filters. 7 years ago when I installed cam also HP oil pump, Oil pressure runs @ 50 PSI. I am not telling anybody they are wrong with remarks I can only go by my experience.
