What is the best oil viscosity to run in a 292 Inline-six with high miles?

[80BrownK10]

I don't do it personally, but years ago, I knew a few people that ran conventional diesel oils such as 15w40 Rotella T or Mobil Delvac for their higher zinc levels. Now that most of the diesel oils have gone through marked changes in recent years, I can't comment on if those zinc levels are still higher than equivalent gas spark ignition oils.

There still a good bit higher than conventional car oils

 

[80BrownK10]

There still a good bit higher than conventional car oils

Just for others reading this oils like rotella 15w40 are also rated for spark ignition vehicles as well. I don't think the most recent rating since most of those are really thin weight oils but all the older ones they rate it for. API certification that is

 

[mikeoverland]

When I had my Buick Regal I used to run Valvoline 20-50 high milage oil in it. Now the way that i drove that car is criminal and i did go through 2 engines (i hated the #1 main cap) but the 20-50 seemed to work fine in San Antonio with the cold, hot, and miserable days that we have down here. I would use it again in a heartbeat but I would aslo listen to the advice that everyone else has given on this subject.

 

[Matt69olds]

When I had my Buick Regal I used to run Valvoline 20-50 high milage oil in it. Now the way that i drove that car is criminal and i did go through 2 engines (i hated the #1 main cap) but the 20-50 seemed to work fine in San Antonio with the cold, hot, and miserable days that we have down here. I would use it again in a heartbeat but I would aslo listen to the advice that everyone else has given on this subject.

One of the tricks to keeping a Olds or Buick together is big bearing clearances. The factory spec is ok for a grocery getter, if your going to beat on it, either make the clearances big enough, or the crank will clearance itself. That’s the biggest reason “rebuilt” Buick/Olds engines don’t last, machine shops treat them like Chevy or ford, with tolerances that work for those engines.

The factory performance olds/Buick engines came factory with bigger clearances. One of Olds sales pitch was “select fit” engine components. If you look at a virgin Olds block, you will see a letter stamp on the deck of each bore. If the bore measured a within a few thousands of spec, it got a A stamp, and used a A piston. If the bore was more than a few thousands, the bore got a “B” stamp, and it got a “B” piston. Same thing with crankshafts and connecting rods. The W-30 select fit engines meant that you put a “B” piston in a “A” bore, and that gave you a few thousandth extra piston to bore clearance. I’m guessing all the engines manufacturers did the same.

In the case of the Buick Stage 1 cars, the oil pumps had heavier relief springs to provide sufficient oil pressure with the bigger bearing clearance. As bad as the oiling system is on a Olds, Buicks are far worse!!! I remember reading a interview with the head engineer of the Buick Stage 1 engine program discussing Buick oil pressure. The question was: how much oil pressure should a Buick have at hot idle? The engineer replied “enough to keep the light off!”

Kinda off subject.

 

[SirRobyn0]

Just for others reading this oils like rotella 15w40 are also rated for spark ignition vehicles as well. I don't think the most recent rating since most of those are really thin weight oils but all the older ones they rate it for. API certification that is

I did a bit of oil research last year, and I agree as a general rule what you just said is correct. I did not even look at thinner diesel oils so I cannot comment on those, but if a person is looking at an engine oil an API certification that starts with the letter C is diesel oil, an oil that is a gas certification starts with the letter S. So an oil approved for both might list the certifications something like this. CK-4, CJ-4 / SP. So those first two certifications are for diesel with the last one for gas.

 

[AuroraGirl]

I did a bit of oil research last year, and I agree as a general rule what you just said is correct. I did not even look at thinner diesel oils so I cannot comment on those, but if a person is looking at an engine oil an API certification that starts with the letter C is diesel oil, an oil that is a gas certification starts with the letter S. So an oil approved for both might list the certifications something like this. CK-4, CJ-4 / SP. So those first two certifications are for diesel with the last one for gas.

SP is a recent certification too, designed to help more with some of the negatives about gas today and a lil zinc if and where needed would be wise with appropiate weight oil.

i think there is something important to remember
Oil is cheap, engines arent, if you change the oil 2 times a year or ever 3-5k with special consideration for more if you use it heavy, you probably cant go wrong. oil can only hold so much in suspension and filters dont filter 100% of oil passing through it, fresh oil is happy, and high mileage inline 6 is thereby happy. if it leaks, that just allows you between changes refreshment of oil properties!

This is all esp important if yours runs a little rich or the rings arent sealing the best-est. May even consider that purple stuff from engine restore. project farm saw compression increase and other good results on his ford tractor, not saying its snake oil or miracle jam but compression is compression :O that means nominally more stuff is staying on the side of the bore where it should????

**** it, amsoil zinc and make sure to put a sticker on the valve cover for good measure

 

[Grit dog]

I did a bit of oil research last year, and I agree as a general rule what you just said is correct. I did not even look at thinner diesel oils so I cannot comment on those, but if a person is looking at an engine oil an API certification that starts with the letter C is diesel oil, an oil that is a gas certification starts with the letter S. So an oil approved for both might list the certifications something like this. CK-4, CJ-4 / SP. So those first two certifications are for diesel with the last one for gas.

And many "diesel" oils are API S_ certified, many do not appear to be, either. However I've used basically whatever is on sale in a dino 15W40 gallon jug interchangeably in everything from a lawn mower to a SRT8 Hemi for at least the last 15 years with ZERO issues.
I even use Rotella T4 or T6 pretty much exclusively in my toys with wet clutches. If T6 can keep an 11,000 rpm 4stroke race bike pulling a snowmobile track healthy for 100 hours and not even need to shim one valve, it is probably good enough for a "loose" old small block or 6 banger...
Only caveats are a special case, like extended drain intervals or specific known issues.

 

[SirRobyn0]

@Grit dog I'm pretty much on the same program you are. 15W40 is a pretty universal oil all my farm equipment, my square, my dodge and other vehicles all get it. The only exception is my wife's van we bought it new in 05 and started it on synthetic and continue to run that.

 

[SirRobyn0]

SP is a recent certification too, designed to help more with some of the negatives about gas today and a lil zinc if and where needed would be wise with appropiate weight oil.

i think there is something important to remember
Oil is cheap, engines arent, if you change the oil 2 times a year or ever 3-5k with special consideration for more if you use it heavy, you probably cant go wrong. oil can only hold so much in suspension and filters dont filter 100% of oil passing through it, fresh oil is happy, and high mileage inline 6 is thereby happy. if it leaks, that just allows you between changes refreshment of oil properties!

This is all esp important if yours runs a little rich or the rings arent sealing the best-est. May even consider that purple stuff from engine restore. project farm saw compression increase and other good results on his ford tractor, not saying its snake oil or miracle jam but compression is compression :O that means nominally more stuff is staying on the side of the bore where it should????

**** it, amsoil zinc and make sure to put a sticker on the valve cover for good measure

You make a lot of really good points and not to get distracted and go down another rabbit hole, but mixture does make a big differance in the life of an engine. We all know being to lean is bad but so is to rich. Even having a choke working properly makes a differance. Most people know a choke to lean or not working tends to lead to a lot of engine revving or pumping of the gas which isn't good, but an excessively rich choke especially if it's to the point that the engine loads up when it's cold will wash down the cylinder walls leading the excessive ring wear.

 

[80BrownK10]

And many "diesel" oils are API S_ certified, many do not appear to be, either. However I've used basically whatever is on sale in a dino 15W40 gallon jug interchangeably in everything from a lawn mower to a SRT8 Hemi for at least the last 15 years with ZERO issues.
I even use Rotella T4 or T6 pretty much exclusively in my toys with wet clutches. If T6 can keep an 11,000 rpm 4stroke race bike pulling a snowmobile track healthy for 100 hours and not even need to shim one valve, it is probably good enough for a "loose" old small block or 6 banger...
Only caveats are a special case, like extended drain intervals or specific known issues.

I too use it in wet clutch ATVs lawnmowers, generators, Tractors , old K10. Cuts down on the amount of types of oil I keep around. I have run a lot of rotella, dello, and lots of Tractors supply company house brand Traveller brand. It was certification CJ for several years longer than other brands.

Our daily drivers are Toyotas. I run the 5w30 that they call for. The Highlander has VVt and needs the correct oil to function correctly. I'm sure there people that have had success with thicker oil but I'm not going to try it. Toyota got it right and makes a good engine and runs fine for hundreds of thousands of miles on 5w30. Our Sequoia is the last year before the 4.7L got the vvt but I still running on 5w30. That engine is reliable and amazing. Plenty of them that have runn 500,000-1,000,000 miles.

 

[Albrigap]

I run Mobil Delvac 15/40 1,000ppm in everything and it got to 15 degrees below zero the other night.
5.3 Chevy LS, 01 Honda Civic, 90 GMC Sub w/ 350.
Shell Rotella 15/40 runs about 1,200 ppm zinc so is one of the few oils left that keeps a flat tappet cam working.
Diesel oil is high detergent which keeps an engine clean and has higher zinc.
Nothing wrong with that.
I have been using diesel oil forever and have never had an oil burning issue.

 

[SirRobyn0]

I too use it in wet clutch ATVs lawnmowers, generators, Tractors , old K10. Cuts down on the amount of types of oil I keep around. I have run a lot of rotella, dello, and lots of Tractors supply company house brand Traveller brand. It was certification CJ for several years longer than other brands.

Our daily drivers are Toyotas. I run the 5w30 that they call for. The Highlander has VVt and needs the correct oil to function correctly. I'm sure there people that have had success with thicker oil but I'm not going to try it. Toyota got it right and makes a good engine and runs fine for hundreds of thousands of miles on 5w30. Our Sequoia is the last year before the 4.7L got the vvt but I still running on 5w30. That engine is reliable and amazing. Plenty of them that have runn 500,000-1,000,000 miles.

Some VVT systems are more prone to problems than others and some are more forgiving but this is just going to be a general statement. At the shop the main oil related issues we see are where there has been long term oil change neglect sludging up the system, followed by wrong oil weight used. The good news is if you put to thick of oil in the engine a simple change fixes it, but I can assure you 15W40 would be to thick for the VVT system to work properly.

 

[80BrownK10]

Some VVT systems are more prone to problems than others and some are more forgiving but this is just going to be a general statement. At the shop the main oil related issues we see are where there has been long term oil change neglect sludging up the system, followed by wrong oil weight used. The good news is if you put to thick of oil in the engine a simple change fixes it, but I can assure you 15W40 would be to thick for the VVT system to work properly.

I figured as much in all these cases. I have the vulnerable known sludge producing 3.0L in the Highlander. So it gets full synthetic oil and 5000 mile changes max.

And on the vvt line of conversation I did have the #1 bank solenoid go bad on it. On the way to work it started stumbling and was ideling all kinds of weird sounding like a misfire and was down on power. It ran ok with minimal misfires the next few times. I pulled both solenoids and sprayed them out with brake clean and reinstalled. Neither looked sludged up. It didn't change the issue. So I ordered a new unit. Doesn't look like Denso makes them so I'm not sure who makes the Toyota OE but I didn't want to install one of the cheap white box parts you see flooding amazon, ebay and rock auto so I chose Gates as my replacement brand . The issue went away and no misfire or stumble since. Not too bad for the original I guess it lasted 260k miles. I'm cheap so I didn't replace bank #2 sensor. I figured there is a good chance it goes out, but I'll deal with it when that day comes. They take like 10 minutes to swap out.