Time for an oil change...
Thread Starter
Burning Brakes
Joined: Jul 2011
Posts: 800
Likes: 15
From: Currently Buffalo NY, originally from MI
Time for an oil change...
Time for an oil change in my 79. Last year I used 10w30 Royal Purple. Planning on Royal Purple again, but I was wondering, what weight would you recommend? Someone recomended 5w30 last year. I went with the 10w30 because it is what I grew up using in everything in my family.
Motor is the stock L48 block, bored .060, and putting out about 435, so its modified quite a bit. What do you guys think?
Motor is the stock L48 block, bored .060, and putting out about 435, so its modified quite a bit. What do you guys think?
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
A 5W-30 oil has the same (or very similar) viscosity as 10W-30 at operating temperatures, while flowing better at cold temperatures.
The only small downside to the 5W-30 is that some oils with a large difference in their cold vs hot viscosities rely on viscosity improvers added to the base stock to give them that wide range.
Viscosity improvers can essentially wear out, so if you try to push your oil change interval too long you might not still have 30 weight oil at operating temps.
Truthfully though, the two grades are close enough that it's not going to be a big difference.
Also, most synthetic oils dont require improvers to meet the 5w-30 range, so the improved cold flow is an improvement with no downside.
Personally, I'm running 0W-40 European spec Mobil 1.
The only small downside to the 5W-30 is that some oils with a large difference in their cold vs hot viscosities rely on viscosity improvers added to the base stock to give them that wide range.
Viscosity improvers can essentially wear out, so if you try to push your oil change interval too long you might not still have 30 weight oil at operating temps.
Truthfully though, the two grades are close enough that it's not going to be a big difference.
Also, most synthetic oils dont require improvers to meet the 5w-30 range, so the improved cold flow is an improvement with no downside.
Personally, I'm running 0W-40 European spec Mobil 1.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
I go with what is manu recommended.
20/50 is good for the temps in SoCal.
Remember, C3 era cars have large clearances
vs todays close (especially at start up) clearances.
Flat tappets vs rollers.
as mentioned, base stock, is the natural state of the oil
until modifiers cause it to ACT like a different weight.
frankly, the EPA mandates have taken the good stuff out of oil. Do you think rollers would be standard if there was oil available to protect flat tappets?
20/50 is good for the temps in SoCal.
Remember, C3 era cars have large clearances
vs todays close (especially at start up) clearances.
Flat tappets vs rollers.
as mentioned, base stock, is the natural state of the oil
until modifiers cause it to ACT like a different weight.
frankly, the EPA mandates have taken the good stuff out of oil. Do you think rollers would be standard if there was oil available to protect flat tappets?
