8.1 Liter gas oil consumption

[Patsslab]

We have a 2004 w22 chassis with an 8.1 liter engine. It would appear that in my first 1000 miles since we bought the unit we used 2 quarts of oil in mixed hwy/round town driving. By Chevrolet standards published in a tcp this is high usage. I now know this is a design flaw with the engines PCP setup but was wondering if anyone has rectified the issue. I did do some searches related to this issue but nothing came up.
Thanks in advance.

[AveryF]

Our 2004 Itasca is also an 8.1 liter engine on a W22 chassis and we typically use a quart of oil every 12-1500 miles so, yes, it does seem 2 quarts every 1000 miles might be a little more than I would expect. It would be interesting to see how much your oil usage varies after another 1000 miles or so. Our mileage is nearly 100% highway/interstate but I'm not sure if your combined highway/city usage figures into the equation, assuming the engine is mechanically sound.

I'm sure one of the Workhorse gurus will be along shortly to offer more help.......

[Flyer15015]

Pat,
How many miles on your coach?
I got mine @ 25K and she is now @ 52K and change.
I run Mobil 1, 10w-40 full synthetic and a can of "Restore" (from Walmart), with every change at about 5K. I've got a lot of respect for that Restore stuff.
Mine runs thru about a quart in 2K miles pounding down the highway pulling a dolly with an '02 Grand caravan attached.
She's got some mod's per my signature, and we generally cruise about 62-65.

Mike in Colorado

[George Schweikle]

That's a pretty thirsty oil appetite. While I don't keep a detailed log, I believe my 2005 8.1, with 70,000 miles, uses much less than a quart every 2000 miles. Towing a car trailer at 65 MPH and in mostly mid-country terrain.

Do you know what weight oil is in your engine?. What mileage?. Somewhere in a Workhorse sub forum post, an owner claimed significant reduction in oil consumption by changing to 10-30 oil, but inexact information since I don't think he stated what weight he changed from, the mileage on his engine, or how he drove the rig. FWIW, GM/Chevrolet are said to have stated the service life of the 8.1 engine is 200,000 miles in RV use.

[JonathonM]

GM put out a TSB for excessive oil consumption of the 8.1L in pickups. I dont know if workhorse put out a similar TSB for the 8.1L but the MH 8.1L is the exact same engine as the truck engine.

The TSB requires the replacement of the intake gaskets if oil consumption is greater than 1 quart every 3000 miles (forgive me if my numbers are a little off; its been a while since I worked for GM). This is supposed to greatly help with oil consumption but not completely fix it. 1/4-1/2 quart every 3000 miles is considered "normal" by GM

I use Rotella T5 5W40. Its designed for high heat and high load applications. Most 8.1's will not burn as much oil if you switch to 10w40 or 5w40 oil. Its "thicker" at hot temperatures and holds up better to the higher loads and higher RPM's experienced in MH's. I burn about 1/2qt oil every 3000 miles and have not replaced the intake gaskets on my motor.

[Patsslab]

I’ll be driving from TX to GA this week. 700 miles on I10. I’ll be checking my oil level every gas stop.

[Patsslab]

22,000 miles. Just completed a tune up. I just bought the coach about 1000 miles ago and don’t have a clue what brand oil is in the engine. From records it’s blended synthetic.

[Patsslab]

5w30 in it presently.

[CamJam1]

I was using a quart of 5w30 every 1,500 miles. Switched to 10w30 based on recommendations of others on this forum and haven't had to add oil between changes ever since.

[yeloduster]

I was using a quart every 1500 miles using Mobil 1 5W30. I switched to Mobil 1 10W30 and still use a quart every 1500 miles.

A quart every 500 miles indicates something needs fixed!

[Mudfrog]

OP, I don't care what the previous owner's maintenance records indicated,, changing the oil would be at the top of my list of things to do. Being winter, maybe go with 10W-30 to see if that helps any.

The manual for my 03 states that straight 30 weight can be used in temperatures above 40°. It's possible that could help a bit. It also contains a warning NOT to use 10W-40 or 10W-50 viscosities.

[JonathonM]

Originally Posted by Mudfrog

It also contains a warning NOT to use 10W-40 or 10W-50 viscosities.

I dont intend to start the great oil debate of 2024 and nor do I like to disagree with the owners manual that was written by a team of informed engineers, but I am inclined to respectfully disagree with part of it in this case.

When understanding viscosity of oil and how use (heat and load) breaks down oil, I use this video from Gale Banks:

https://www.youtube.com/watch?v=9rEGIB2F8qA

It provides a FANTASTIC explanation of how viscosity is diminished by heat and load.

In an engine designed for 5W30, 5W40 will provide greater separation/lubrication between surfaces but will:
A) experience greater molecular sheer on the oil viscosity modifiers; which will cause it (5W40) to break down faster.
B) build greater heat than 5W30; which will cause it (5W40) to break down faster.

When I worked for GM as a technician, the general observation and consensus amongst techs was that 5W30 provided great lubrication until the viscosity began to diminish. The viscosity would appear to diminish quicker than GM intended, after long periods of high load and high heat. As the viscosity would diminish, the oil became "thinner". 5W30 becomes 5W29... 5W28... 5W27... etc...
Gale Banks provides a great explanation of this starting at 33:00 in the video above.

We noticed that even after performing the TSB repairs on the 8.1L, trucks that saw heavy use still experienced oil consumption. We started using 5W40 and the oil consumption was greatly diminished. Some fleet managers liked 10W40 because it was cheaper. However, we didn't like using 10W40 during the winter because of its lesser start-up properties. 5W40 seemed to provide good protection at cold temperatures and sufficient protection (better than 5W30) at high temperature. Please keep in mind that this was in Phoenix, where high ambient temps cause even higher oil temps.

[Patsslab]

I drove 600 miles Tuesday on I10 at 58 mph, pulling a Ridgeline on a tow Dolly with no oil loss. Tomorrows leg of the trip will be 280 miles on I10 and the last 200 miles on backroads. We will see what happens.
Thanks to all for your input.

[KarolinaTom]

I change my oil at 3k miles and always use synthetic, although I am not particular on the brand, provided it is Dexos1 rated.

I use virtually no oil on a flat drive, but can consume 1/4 to 1/3 quart in heavy mountain driving. My drives top out at 400 to 500 miles in a day, and I check / top off each morning.

Oil consumption is more noticeable above 2000 miles, and less noticeable when fresh. 5W30 is all I have used. 91k miles, owned since 55k miles.

Tom