71dusterman
Well-known member
Kind of a open question. What is better for engine longevity. Engine oil that has a higher temp than the engine coolant or lower, what is better for all round engine performance and engine life. 
Oil cooling.
- Thread starter 71dusterman
- Start date
68R/T
I got drunk and swallowed my teeth, now
You never will get oil temp lower than coolant. The oiling system has more cooling effect on the engine than the cooling system itself. The cooling system is used primarily to maintain a constant temp. Keeping your oil on the cooler end makes the cooling systems job a little easier. Your oil needs to reach at least 212 deg. to "burn" off any moisture, but its' additives start breaking down at 275 deg. Ideal oil temp is 230 to 250 deg.
Dr.Jass
Pastor of Muppets
This is not correct. The coolant has far more effect on the engine temperature than the oil does, which is why the chambers (the primary source of heat in an engine, by a long shot) and cylinders are cooled by liquid (or air) rather than oil. Oil's primary function is lubrication, while its cooling effect is essentially a bonus. Oil is not exposed to the truly-hot surfaces of the engine; a rotating crankshaft or cam simply doesn't get terribly warm due to the lubricity oil provides. This is why the vast majority of cars don't have an oil cooling system; in most cases the oil will never reach 270° without one. Adding a ginormous-by-huge oil cooler will not solve an overheating issue in most cases.
As far as performance and longevity, you've simply got to choose which one is more important. As 68R/T stated, ideal oil temperature is generally in the 230-260° range. Towards the upper end of that scale (and beyond) is where you find better peformance, while at the bottom is where the longevity lies. You could get your oil temps lower than coolant temp with a huge oil capacity and large cooling loop, but at those temperatures it creates sludge. So even though the oxidation rate for pure petroleum doubles for every ~20° beyond 150°F, a little heat is a good thing. Besides, the additive package lowers the oil's tendency to oxidize so quickly.
Another aspect of oil temperature is its effect on flow. The hotter the oil, the better it flows and the easier it is to pump through the engine. Hot oil means free horsepower due to lower pumping losses, which is why many professional circuit racers run their oil hot (300° or more) as well as lightweight--the heaviest oil you'll find in a NASCAR pit is 5W-30, and that would be at a superspeedway. In qualifying, they'll run as low as 0W-10 depending on track length. Testing has been done with synthetics, both in the lab and on the track, at temps as high as 350°! Of course, you can't buy the oil they use, and they rebuild the engines after every event. This approach isn't exactly a street-oriented idea, but at the same time, sub-coolant oil temperatures would actually have an observable negative affect on fuel economy.
Many large over-the-road diesels actually use an oil thermostat to route oil through the cooler. Now, those guys need to not only get every mile possible out of their oil, they absolutely need to get every mile out of the engine itself. They're also measuring their fuel economy in tenths of a MPG. Those oil thermostats open the cooling loop around 255°F and close (bypassing the cooler) around 235°F and below.
Unless you've got something in your combination that would generate ridiculous heat in your oil, such as high bearing surface speeds (due to sustained high RPM and/or really-large bearing journals), turbochargers, etc. oil cooling probably isn't necessary. If you want one for piece of mind, that's fine, but don't go crazy with one big enough to block the radiator. If you're looking to monitor it, the standard place to check it is at the point where the outlet to the cooler would be, in this case right at the outlet of the oil pump (the same is true of transmission-temp gauges; they should be in the "hot" line to the cooler as close to the transmission as possible).
Use good oil. Change it regularly, either 3,000 miles or the manufacturer's recommended interval. Oil in a carbureted or even TBI engine should be changed every three to four months regardless of mileage; carbs/TBIs dump fuel into the oil and break it down much more quickly than port-injected vehicles do. Obviously, if you change the oil and park it for the winter shortly thereafter, there's no need to change again it come springtime, but if it's being operated fairly regularly, that oil's breaking down in the pan even while parked. Used oil contains corrosive agents and absorbs moisture much better than fresh oil, so if you store your car for months at a time, change the oil before you park it, rather than when you bust it out from under the cover. Or, do both. Oil's cheap. Engines aren't.
restoman
The paint fumes have cleared so I'm
The only thing I could add to Doc's info is that most Nascar teams use a straight grade oil, not multi-viscosity and even though the engines are torn down after every race, they run the same engine through the entire race weekend - practice, qualifying and racing - it bears mentioning that last year the team of Joe Gibbs #20 of Matt Kenseth ran the entire season without an oil related engine failure. Most teams do. That's some pretty stellar racing oil Joe Gibbs uses, developed in-house specifically for themselves. Synthetic, of course...
FYI, the old Cascar racing series engines all used Castrol 50 racing oil, but they ran on tracks less than 3/4 of a mile in length, and those engines got HOT!
FYI, the old Cascar racing series engines all used Castrol 50 racing oil, but they ran on tracks less than 3/4 of a mile in length, and those engines got HOT!
Dr.Jass
Pastor of Muppets
I had occasion twice in 2011 to speak with four different then-current/former crew members of JGR. To a man, they told me they run multigrade in the race cars, in various light weights. Apparently some teams qualify in cooler weather on straight 0W. Anyhow, I mentioned the 20W-50/straight-50W phenomenon still happening at the local 1/3-mile paved oval, and one of them quipped, "Why are they still running gear lube in their engines? We quit doing that decades ago." 
Kenseth not having an oil-related failure is important, considering Joe Gibbs' heavy involvement in marketing his own motor oil. I've no doubt it's excellent stuff but have not switched from Royal Purple. One thing you can be assured of, though: Mobil 1's marketing campaign about NASCAR is misleading. The stuff they use in the pits is not available to the general public. It's literally NASCAR-only, with F1 and other series having formulations of their own that we also can't have. I'm guessing part of that has to do with the increased oil temps, for which the formulation might actually cause sludge at street-engine temperatures.
Kenseth not having an oil-related failure is important, considering Joe Gibbs' heavy involvement in marketing his own motor oil. I've no doubt it's excellent stuff but have not switched from Royal Purple. One thing you can be assured of, though: Mobil 1's marketing campaign about NASCAR is misleading. The stuff they use in the pits is not available to the general public. It's literally NASCAR-only, with F1 and other series having formulations of their own that we also can't have. I'm guessing part of that has to do with the increased oil temps, for which the formulation might actually cause sludge at street-engine temperatures.
71dusterman
Well-known member
Jass, I was hoping you would pop in on this. The reason I was asking was because I have a 2015 1500 Ecodiesel and oil temp is always front and center as it cools the turbo and turbo life is what helps keep engine life strong. I am new to the diesel world so lots to learn. Just fyi the Eco uses 10.5 qts in the sump. I love the power and economy that the Eco gives compared to what my 07 Mega Cab with the 5.7 Hemi. Around 33mpg in the Eco highway compared to the 16.5 the Mega got is hard to pass up.
restoman
The paint fumes have cleared so I'm
The machining and metallurgy differences between the Nascar engines and just about anyone else running short tracks are huge... even the old Cascar series basically used stock blocks and cranks. Nothing in a Nascar engine is stock, except maybe the manufacturer logo stamped into the parts. 
They might still be pushrod V8s but they're really high tech, purely race pieces.
Very few of the teams experience oil-related failures. The only one I can think of last year is one of RCR's cars chucking some rods out the bottom at a short track, after spinning the engine backwards in a spin earlier in the race. Valve springs seem to be the only weak link in those $100 k mills...
Quaker State and Valvoline both took a lot of heat years ago for their advertising campaigns using Nascar teams. Hendrick uses Quaker State products but Valvoline became strictly a sponsor and doesn't infer that their slippery stuff is in the sump of the car anymore.
I've been using Royal Purple since switching from Amsoil after the shop closed... love it. I'd dearly love to put it in the crankcase of the old Beetle, but I think it would run out faster than I could pour it in.
They might still be pushrod V8s but they're really high tech, purely race pieces. Very few of the teams experience oil-related failures. The only one I can think of last year is one of RCR's cars chucking some rods out the bottom at a short track, after spinning the engine backwards in a spin earlier in the race. Valve springs seem to be the only weak link in those $100 k mills...
Quaker State and Valvoline both took a lot of heat years ago for their advertising campaigns using Nascar teams. Hendrick uses Quaker State products but Valvoline became strictly a sponsor and doesn't infer that their slippery stuff is in the sump of the car anymore.
I've been using Royal Purple since switching from Amsoil after the shop closed... love it. I'd dearly love to put it in the crankcase of the old Beetle, but I think it would run out faster than I could pour it in.