The Stovebolt Site Forums The Shop Area Engine Shop proper oil for my new to me 1950 Chevy with a 1961 261

Greetings, new member here. I have a recently-purchased '50 Chevy with a '61 261 engine. The previous owner has been using Rotella diesel oil, T5, 10-40. I noticed that the oil pressure was around 20 when going 50 mph. Is this perilously low? Is diesel oil recommended? If no, a) dino oil, b) synthetic, or c) Valvoline VR 1? Any other tips for the care and feeding of this engine is appreciated. Thanks, Larry

Welcome to Stovebolt Larry!

I've got Rotella Diesel Grade 15W40 in my '54 235 powering my 1951 3100. Your oil pressure reading isn't terribly unusual. I think lots of fellow Stovebolters use Rotella. The oil topic has been discussed a ton over the years and you can find many of those conversations by using our Search the Site link to pull them up and read through the previous conversations.

Once again - Welcome!

A half dozen years on this site and with pm discussions with with those who you will learn to trust…
15/40 desiel rated oil is a great choice…
Takeaway is that less than 15 on the lower number is thin for these engines.
I would be interested to see what running pressure change if any you get by switching to 15/40.

Chuck

Here is my experience with Rotella and the 235 engine in my ’53 truck. For 10 years I have annually changed the oil using RotellaT4 (Dino) 15w-40. No appreciable oil use, no noticeable leaks and good oil pressure. Last year I mistakenly picked up RotellaT5 (semi-synthetic) for the annual change. During the summer, I noticed slight seepage around the lifter cover and under the manifold. Coincidence? Last month. I changed oil again, this time ensuring it was Rotella T4 (dino) and for good measure I added a quart of Lucas gasket treatment additive. Its been less than 200 miles but the engine has remained dry, and the oil pressure is even better, remaining at 3/4 to pegged even at idle.

I used to run 15W40 diesel oil in my 235. It gave me no issues, but I’ve since learned that the higher detergent levels in diesel oil are somewhat antagonistic to the ZDDP.

Last couple years, I’ve run VR-1 20W50. It’s not a great deal more expensive, has plenty of ZDDP, without the high detergent levels. Peace of mind, if nothing else.

My truck has always pegged the oil pressure gauge at any rpm above idle and been somewhat low at hot idle (10-15 psi). I haven’t noticed much of any difference in that since switching to the 20w-50.

Thanks to all, I'm wondering now about using the VR-1 , which I use in some other cars (10-30 weight). The VR-1 is 20-50, the Rotella's dino and semi-syn are 15-40. I'm trying not to be hyper about oil choice, but I don't want to screw up (which is the usual result). Engine is new to me without much background info. except a '61 out of a 3/4 ton truck. On a side note, I pulled the plugs to change and they were at .078. .035 is recommended?

VR-1 is available in quite a few viscosities. 10W-30 and 20W-50 as well as multiple straight viscosities SAE 30 thru 60.

I use 20w -50 frequently in some of my old vehicles as well as 15w-40. Either one will be fine for your engine.

Spark plug gap should be in the .035 - .040 range. .040 is optimal.

larry - That wide spark plug gap could mean a PO (previous owner) installed an HEI distributor (the HEI modified original distributors have a small cap that make them look very much like an original distributor). I'd do some closer inspection of what you have before you change the gaps. An HEI distributor will work best with the proper larger than stock spark plug gap.

My original manual calls for single-weight either SAE-20 or SAE-30, as multi-weight oils were just becoming popular in the 1950s. The second number is most important with multi-viscosity oil as that is what you have after start and warm-up. Even more important with these engines with primitive or no oil filtration and poor crankcase ventilation is regular changing of the oil every 1,000 -1,500 miles, or annually whichever comes first.

Gdads51, you probably saved me a boatload of grief. The distributor is red but fairly large. There is no manufacturer or any indication of HEI or an upgraded stock-size unit. With plugs at around .080 must be HEI. Thanks, Larry

There was a time when Rotella was an alternative because of the ZDDP package. But the market has caught up to the old car hobby and the need for a better auto formulated lubricant with the appropriate ZDDP package. That, and the formulation for Rotella has changed over the last couple of years. Add to that the fact that the oil is specifically formulated for diesel engine use and not automotive use. There are a lot of opinions. But mine is no, you have better alternatives and with the cost of parts and machine work, probably better to use oil specifically designed for an old automotive engine.

https://www.onallcylinders.com/2025...-blame-for-my-premature-lifter-failures/

I have never run Rotella myself just for that reason, but I have long run the Brad Penn 10W30, which is now called Penn Grade 1. I am hard on my inline motors. This past August I ran a car in competition at the Trifive Nationals and zinged my 261 motor up to 5800 rpm all week on the dragstrip and not a moments issue. I won my class, the first and only inline powered trifive to ever win its class at that show in the decade they have been running it. I broke the motor in with the Penn Grade 1 break in oil. It’s essentially the old Kendal 1 high performance oil (refined in Bradford pa). I use the 10w30. It’s a semi synthetic which means it uses Pennsylvania base stock which is still refined in the old Kendal refinery in Bradford pa, and then blended with a modern additive packages

https://penngrade1.com/products/high-performance-oils/

There are also other alternatives, Driven, Gibbs, Hemmings, and others also now offer oil specifically for old motors.

I know a lot of guys swear by the stuff. A lot of times because it’s cheap. Not me. I want something that is in fact engineered for old car use.

Nothing really wrong with using Rotella in a gas engine, either old or modern. An engine is really just an engine.
Rotella T-4 has the following API specifications: CK-4, CJ-4, CI-4 Plus, CI-4, CH-4, SN. The SN is the gas engine approval, so anything with an S_ approval could be used in an old engine. Yes, ZDDP has been reduced in the last few years in ALL the diesel oils, and likely in gas engine approved oils as well. [on edit] attached is a snip of oil analysis results on my diesel truck using conventional 15W-40 oil. You can see that the reduction happened around 2018.
That being said, I plan on using VR-1 oil in my engine, which supposedly has higher ZDDP than the "normal" gas engine oils you'd find on the shelf at Walmart or wherever.

Another motor oil especially for antique cars and was developed and is sold by the Classic Car Club of America.

It has 1600ppm ZDDP and is 15w-40.

www.inrccca.org

Speaking of......I've been using VR-1 straight 30 weight in my '62 - 235 for years but now have developed a few leaks and wonder if I should go VR-1 20w-50. Hmmmmm..

Sorry to Larrymaine, I don't mean to be stealing this thread. Can start a new one if preferred.

Having watched "The Motor Oil Geek" on Youtube a bunch, I've come to believe that the diesel formulated oils are best left to diesels. The reason is the high level of calcium that is used as a soot dispersant. That wouldn't be a problem except that it competes with ZDDP for the spaces in the metal pores, which is a problem on flat-tappet cams. I believe all the engines that spec the various API CK oils have roller lifters. I have run DELO in mine and after I didn't get it free anymore switched to Rotella T3. When I had the engine apart after 100,000 mi. to put that cam in another engine, I could tell there was some cam and lifter wear. Not enough wear to stop me from reusing the parts but I could see it. I am now using Castrol GTX classic with the high zinc additive package -- 20-50 in summer and now 10-40 for winter (goes below zero F here frequently).

Yes I seen that video as well and agree .I only used the retell for a few oil changes and did not put many miles on so when my truck gets back on its feet I will change back also.Thanks will try the castor oil gtx .

I agree, Castrol GTX Classic looks to be the perfect conventional oil for the stovebolt engine. Spec sheet reads that it is specifically made for pre-catalytic converter classic vehicles requiring zinc and phosphorus additives. Great timing as well, - AutoZone has it on sale this week for $5.99 regularly $9.49 per quart.

Got some GTX Classic 20-50 today to try. Thanks for the suggestions.

Take this with however many grains of salt as you will, but that 261 of yours does not need 20w50. 10w30, 10w40. Remember, these motors were engineered for 30 wt. unless your motor is really worn out, or the bearing clearances are excessive, you need flow for the bearing cushion.

Mike,
Does that apply also to a 235 as well? The only reason I was considering going to 20w-50 was due to a few little leaks and thought 20w-50 would help.

Craig,

20w-50 significantly slowed/stopped leaks on my Cadillac. It will be fine for a 235. I also use it in the 216.

For what it's worth, here's a snip from the 1955 2nd Series Factory Service Manual regarding oil viscosities:

And don't forget to cut the straight 30 weight with 10% kerosene for winter operation.

Nearly 50 years of playing with these 235 and 261 motors and I have never run oil that thick. All of these motors leak a little. But proper oil flow is both a cushion between the journals and the bearings, valve tips, gears, other parts, but also acts as a coolant. So the idea is to have oil flow through the bearings. I run my 235 and 261 motors really hard. Harder than most. I just won the street tire drag class at the Trifive Nationals in Bowling Green Kentucky this past August in a trifive powered by a 261. First time an inline has run in the actual competition and first time ever for an inline to with a class. I zinged the 261 pretty good, up to 5800 rpm. I run 10W30 Penn Grade 1 (the former Brad Penn, which is itself the former Kendal 1 oil from back in the day). Before the oil formulations changed and eliminated the ZDDP I need for my cams, I rang Quaker State and Pennzoil, also 10W30. If I am working on an older motor, I might go 10W40 if I think the bearings are worn enough to need the slightly thicker oil.

Others run the heaver weight oils, straight weights, full synthetics, or the Rotella diesel oil and swear by the stuff. I have been racing and being hard on 235s and 261s for most of my life. And truth be told, I have not had any oil related issues so I tend to stick with what works.

But that is just me.

I use the heavy weight oil in my vehicles that have their original, un-rebuilt, leaky, high mileage engines. If I were to rebuild the 216, I'd use 10w-30.