Oil Grade in Long Haul Trucks

[Gary in Sandy Eggo]

I'm fascinated that long haul trucks use multi-grade oils. Regardless of brand or type, multi-grade oils will lose viscosity over time due to polymer shear.

I can see where cars with frequent cold starts and short trips and frequent oil changes benefit from multi-grade oils, but a long-haul tractor engines run 8-12 hours minimum per cold start, and oil change intervals are in the 10's of thousands of miles.

Why don't long haul tractors run straight SAE-30 or SAE-40 depending on whether it's summer or winter? The single-weight oils are far superior from a lubrication standpoint. Inquiring minds wonder???

Regards, Gary in Sandy Eggo

 

[Steve S]

'Because the 15w/40's work so well. When I drove trucks Cummins used straight 30 and the Detroit 2 cycles used straight 40. What is interesting about the trucking industry is that engine and drive line life is paramount so what works is what is used.No foam or K
@N filters used.

 

[Chris142]

The multi weight work well. Many engine go 1M miles and more w/o a rebuild.

K&N used to make air filters for big trucks and equipment. Wonder how long the engines last then?

 

[1040 WreckerMan]

40 wt oil is still used in some Detroit’s, although most modern designs use 15w40 in the industry as a standard. 750K on a long haul truck is fairly common and I've seen plenty with 1m+. Modern 15w40 HDEO are an excellent formulation compared to technology of days gone by.

The oil coolers in these engines can take 200-250dF engine oil from high load operation and cool it down to 100dF (or less depending on ambient) when they idle. 15w40 produces less wear than a 40wt at cooler temps generally. Long haulers idle trucks for long periods usually when they are unloading or laying over at a rest area or truck stop.

I think that modern 15w40's probably don't shear out of grade in an amount of any significance over a 40wt. Even the 40wt will shear some.

With the size air filters most trucks have, airflow isn't a problem. Although I have seen 250 Cummins re-powered with 8V92TTA with the 250 Cummins air filter left installed = lots of smoke

 

[bruce381]

Oil shear now days is not a big deal, also since most UOA,s do not include the orignial oil as a baseline it is hard to say how much shear or fuel dilution is taking place.

Everyone has a cow if the used oil is .1 cSt under whatever grade it is suposed to be. But with out a New oil baseline the oil may have been on the low side new.
bruce

 

[Ken2]

Cheap viscosity index improvers shear a lot. Top quality, higher cost viscosity index improvers shear very little. Diesel engine oil is made to be much more robust than most passenger car motor oil.


Ken

 

[androbot2084]

Some of the new synthetic oils are dual rated multigrade and straight grade combined. For example there are dual rated 10w30/SAE30 and dual rated 20w40/SAE40 engine oils available. So now consumers get the best of both worlds the shear stability of a straight grade and the wide temperature performance of a multigrade. The Mobilguard 1 20w40/SAE 40 synthetic oil works great in a Detroit Diesel 2 stroke. And Quicksilver makes a petroleum 25w40/SAE40 thats pretty good.

 

[androbot2084]

When truckers encounter temperatures under 0 degrees F some of the truckers are using 5w40 synthetic instead of 15w40 petroleum. This way the truckers save fuel because they can shut down the rig in cold weather without worrying about starting up the truck. Since synthetics are so expensive a lot of truckers use a group III synthetic like Shell Rotella 5w40 because it is cheaper. Synthetic blends like Shell Rotella 10w40 are also available which offer better cold weather performance.

 

[androbot2084]

Since most trucking fleets do not have Detroit Diesel 2 strokes Truckers have little need for a straight SAE 40 grade oil. Therefore most truckers use 15w40 petroleum oil. But for subzero temperatures 5w40 synthetic heavy duty diesel oil is the only way to go according to the OEM's.

 

[KICK]

old detroit 2 strokes are about the only engines that still require straight grade Lube oil. they need a an ash contnet in a specific range or the liner ports tend to get deposits.

everybody specs 15w 40 now. it works. easier starts and more oil flow at low temps.

 

[salesrep]

Many of our long-time belivers in the 15-40 syn-blend are switching to our 9000 sereies syn 5-40.
Better cold pumping and the biggest reason is the 1.5% fuel economy gain 5-40 gives you.