First post from a new member. I'm putting a vintage (1930's) vehicle back on the road and would appreciate the forum's collective wisdom on engine oil.
The engine is an air cooled, in-line 4 cylinder that shares its oil with the transmission. The clutch is dry. The engine has a crude, wire mesh sump oil filter so oil changes will be made at 500-1000 mile intervals. The cost of oil isn't really a consideration as the vehicle won't be used on a regular basis.
The factory recommendation was for straight 20W in the winter (40F and to below freezing), straight 30W for summer, and straight 40W for continuous operation in >80F temperatures. Of course oil technologies have come a long way since the 30's.
I've spoken with someone who has has owned and operated several identical vehicles for decades, and he uses 10W-40 year round in temperatures from about 40F in the winter to 95F in the summer. Based on the factory specs, it seems like 15W-40 would be a better choice in an off-the-shelf product, but he hasn't experienced any ill effects using 10W-40. My ambient operating temperature range would be about the same. I was explicitly warned not to use straight 40W in cooler temperatures as other owners have experienced big end bearing failures with that combination.
Based on the factory specs, it seems like a low end of 20-25 and a high end of 35-40 would be optimal for my use, but those are not available off the shelf. So I'm wondering whether I could get there by mixing 15W-40 and straight 30W or 40W?
Another reason for wanting to go with a mixture is that the engine was probably operated with non-detergent oils for a long time, and I'm a little concerned that switching to a detergent type multi-weight oil will suddenly release sludge deposits. Whereas if I mix a non-detergent single weight and a detergent multi-weight, the overall detergent concentration will be lower such that sludge deposits will be released at a slower rate, which can be accommodated with very frequent oil changes during the first 1000 miles or so.
Mixing Multi-Weight and Straight Weight
- Thread starter SteveCr
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Well first off the "W" portion is not a viscosity, it is a cold-cranking specification. So you don't get there by mixing oils. The "low end" as you call it isn't determined that way, at least in terms of what "W" rating is obtained.
As for which multi-grade 40 oil to use, either one would work well in your climate. It won't make any difference. There are a lot of decent 15W-40 heavy duty engine oils (HDEO) that would work.
And does the engine have sludge? Have you seen it in the engine? If it does exist, detergent oil isn't going to make it drop off in large quantities like some engine flush products would do. You should be good to go.
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And does the engine have sludge? Have you seen it in the engine?
A regular 10w40 should cover everything without any mixing.
You have to be careful in your terminology. There are actually winter grade oils that are designated 20W and 25W. A 20W winter grade oil is not the same as a 20 monograde. Years ago, there was actually a multigrade oil that was 20W-20. This meant it met cold cranking and pumping specifications for a 20W oil, and viscosity at 100C for a 20 grade oil.
If your friend that has the same car has had success with 10W-40 oil for many years, it's probably OK to use.
My preference would be a 15W-40. I wouldn't use a non-detergent oil, but I would drain it every few hours of operation to see how quickly it's cleaning the sludge. The operation you did cleaning the sump with the diesel fuel was probably pretty effective. But the first oil fill after that may be subject to thinning if there is much diesel left in the nooks and crannies.
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I wouldn't use a non-detergent oil, but I would drain it every few hours of operation to see how quickly it's cleaning the sludge. The operation you did cleaning the sump with the diesel fuel was probably pretty effective. But the first oil fill after that may be subject to thinning if there is much diesel left in the nooks and crannies.
Here's a pic of the vehicle in question, a Nimbus Model C. It's actually a 1952, but the engine was first manufactured in the 30's and the design didn't change until end of production on 1960.I've had a roughly 50-50 mix of straight 40 and 15W40 in my (3-cyl liquid cooled car) engine for about 3 years.
It was an emergency response to an oil leak, and I might not have done it deliberately, but it seems to be fine.
I assume its more shear resistant (though that's unlikely to be much of an issue for either of us), and perhaps gives me something like a 20/50, though there's no way to calculate that.
In your situation, keeping an eye on it, and with very frequent drains, its very unlikely to be a problem, but there's unlikely to be any huge advantage either, and simply using a 15/40 is, well, simpler.
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I would at least drop the pan and scrape out the sludge you will find there. Otherwise you will be chewing away at that layer of crud for a very long time. The diesel you poured in the not running engine and then sloshed around just looked like it was effective. Don't take much sludge to turn oil or diesel black.
Lots of very short change intervals is a slow and expensive method.
Better to strip and scrape, it's quicker and cheaper.
Originally Posted By: SteveCr
First post from a new member. I'm putting a vintage (1930's) vehicle back on the road and would appreciate the forum's collective wisdom on engine oil.
The engine is an air cooled, in-line 4 cylinder that shares its oil with the transmission. The clutch is dry. The engine has a crude, wire mesh sump oil filter so oil changes will be made at 500-1000 mile intervals. The cost of oil isn't really a consideration as the vehicle won't be used on a regular basis.
The factory recommendation was for straight 20W in the winter (40F and to below freezing), straight 30W for summer, and straight 40W for continuous operation in >80F temperatures. Of course oil technologies have come a long way since the 30's.
I've spoken with someone who has has owned and operated several identical vehicles for decades, and he uses 10W-40 year round in temperatures from about 40F in the winter to 95F in the summer. Based on the factory specs, it seems like 15W-40 would be a better choice in an off-the-shelf product, but he hasn't experienced any ill effects using 10W-40. My ambient operating temperature range would be about the same. I was explicitly warned not to use straight 40W in cooler temperatures as other owners have experienced big end bearing failures with that combination.
Based on the factory specs, it seems like a low end of 20-25 and a high end of 35-40 would be optimal for my use, but those are not available off the shelf. So I'm wondering whether I could get there by mixing 15W-40 and straight 30W or 40W?
Another reason for wanting to go with a mixture is that the engine was probably operated with non-detergent oils for a long time, and I'm a little concerned that switching to a detergent type multi-weight oil will suddenly release sludge deposits. Whereas if I mix a non-detergent single weight and a detergent multi-weight, the overall detergent concentration will be lower such that sludge deposits will be released at a slower rate, which can be accommodated with very frequent oil changes during the first 1000 miles or so.
Originally Posted By: Olas
Lots of very short change intervals is a slow and expensive method.
Better to strip and scrape, it's quicker and cheaper.
nice bike--bet it was fun to work on it.
IMO WMT SuperTech or Rotella 15-40 will do ya fine
Steve
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