Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 12, 2025 ...

6V92 NAPA Oil

April 08, 2021, 12:26:02 pm

I am ready to change the oil on our 6V92. I have misplaced the NAPA part# for the correct oil.
Does anyone have it?

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Re: 6V92 NAPA Oil

Reply #1 – April 08, 2021, 12:49:06 pm

Most use Delo 100, 40 wt.  Others with the same 2 stroke will chime in.

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Re: 6V92 NAPA Oil

Reply #2 – April 08, 2021, 02:11:41 pm

Bretts correct Chevron Delo 100 40 wt. Make sure it's  Delo 100 not Delo 400. 100 is low ash and made for 2 stroke engines.
Oreillys part #100-40-1.
3 gallons per case. They will make you order full case quantities. 

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Re: 6V92 NAPA Oil

Reply #3 – April 08, 2021, 03:09:33 pm

Here's the list of low ash 40 or 50wt oils suitable for Detroit 2 cycle engines from Tejas Coach Works.  Tejas Coach Works Factory DDC Oil Information Data Page

They are liquidating their assets from the last 40 years.  Some great deals on Detroit parts. 

Let's keep these old buses and Foretravels alive and still rolling!

Jerry

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Re: 6V92 NAPA Oil

Reply #4 – April 08, 2021, 03:12:12 pm

It takes 5.5 gallons for a change with filter. I buy 7 gallons and keep one on board for trips. I changed before a NorCal to Hilton Head Island and return (6000 miles) and used 2.5 quarts by the time we got back.

Most car parts stores can order it or any marina will have it. Shell Rotella T1 #40 will do it or if you find it, Shell Rotella DD+ #40. Less than 0.8% ash. Shell says the low ash keeps exhaust valve deposits to a minimum. Very low EGTs in a 2 cycle may be the reason.

If you have not changed oil before, buy a good strap wrench as in my old post, try loosening a tiny bit to make sure it moves (Brett's suggestion), puncture the bottom and drain the filter. Follow the directions printed on the side of the filter for installation. Do NOT over tighten. Good to install a low profile quick drain so you can start/stop the hot oil while draining.

Pierce

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Re: 6V92 NAPA Oil

Reply #5 – April 08, 2021, 08:47:04 pm

Mike,
It's also a good time to take a sample and get an oil analysis if you haven't already. I use Blackstone Laboratories. Blackstone Laboratories

They give you a complete report with recommendations.  The report will show wear metal averages, sodium level from coolant, and fuel dilution percentage.  Test kits are free!

I have done this twice since owning the coach and now it's time for another test since I will be changing the oil also. 

On mine at 84500, I didn't know how many miles were on the current oil.  The first test showed wear levels typical for this type of engine after about 7800 miles on the oil.  I changed the oil and the second test after 3000+ miles showed a significant improvement in all areas, especially fuel dilution. They did find  a lot of silicon.

"This could coming from the air filtration system (including all of the hoses and fittings) or from a harmless sealer, lube, or additive.  Fuel dilution went down from 3.0 to 0.5% - a nice improvement.  We'd change this oil and stick with 3000 miles for the next change." 

Testing the oil will give you a good baseline on the current health of the engine and a heads up on potential problems.  Diesel Engine | Blackstone Laboratories

Jerry

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Re: 6V92 NAPA Oil

Reply #6 – April 09, 2021, 12:46:46 am

Jerry has a good explanation of what a oil sample can show you. One of the biggest threats your Detroit has is the air cleaner or rather the air cleaner intake routing. Whoever designed the air cleaner intake location needed to be committed to Bedlam. U280s and U300s take the engine's air from right behind the right rear wheels where all the road debris and water can be ingested. It's much worse on the U300 with the Detroit as the 2 cycle uses much much more air than the Cummins. The holes in side of the cylinders and the four exhaust valves for each cylinder mean that it has a huge appetite for air. Both have turbos but the Detroit has a big positive displacement blower right below the turbo. The fact that the 2 cycle is firing twice as often at the same RPM on each cylinder means that it's sucking up anything the wheels throw back including rain. I even found small branches in our filter canister. The rear tires break the branches into smaller pieces and the convenient intake sucks them in.

The translation here is short air cleaner life and if the air cleaner gets wet, the Detroit will cause it to collapse and let all the dirt go straight into the engine. This is called "dusting" the engine and quickly causes bore wear. Unless you are handy at a liner/piston swap, it's going to be very expensive.

Foretravel mostly cured this in the later 1993 GV models but if you don't have one of these, you need to constantly check the restriction minder on on your 1992. As seen in my post from last year, the quality of construction in air filters is important. The one that partially collapsed in ours was a Wix but the Donaldson I replaced it with was much better reinforced and constructed.

When I took our filter out the first time, I could not see the filter from all the dirt and debris on it. The difference in power was noticeable. We take ours on gravel roads quite a bit so have to change filters frequently. Best is to modify the intake to match the late 1993 models.

Jerry, will give you a call tomorrow.

Pierce

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Re: 6V92 NAPA Oil

Reply #7 – April 09, 2021, 04:57:56 pm

Not only is using the correct oil and periodic testing for Detroit 2 cycles vital,  I found a couple of videos from the Bus Grease Monkey on what can happen as a result of overheating, in this case from a faulty thermostat on one side.  It's a big heavy 92 Wanderlodge with an 8v92TA DDEC II software level 154.  He also found a bad injector, all resulting in missing, low power, smoking, scored and cracked liners and an in-frame overhaul!

Watch Scott the Bus Grease Monkey use the Pro-Link to retrieve the historical codes on the overheating.  I was surprised the owner said he never got an overheat warning on the dash.  There were 39 High coolant temperature situations in the history and this was probably over a long period of time.  Also, running injector tests and cylinder cut-out tests would have alerted him to look for potential problems with the bad injector and loss of power before this catastrophic failure. 

https://www.youtube.com/watch?v=55xslvhSwu4

https://www.youtube.com/watch?v=mRB2tZqVOwk

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Re: 6V92 NAPA Oil

Reply #8 – April 20, 2021, 11:14:05 pm

Here's the rest of the rebuild with test drive and also a video on a rebuild of the water pump from Tyler (Indiana Diesel).  The thermostats were replaced with 170s. 
 
I learned that the DDEC takes an average of both temp sensors. A faulty thermostat could result in one side running much hotter than the other causing major problems over time. 

Having separate gauges for each temp sensor would be a good idea.

An inline temp sensor from the lower radiator hose might be a good idea also to monitor radiator cooling efficiency,

My dash gauge always reads different from the coolant temp checked with the Pro-Link.


https://www.youtube.com/watch?v=1pvKVd21TDo

https://www.youtube.com/watch?v=27r9Z2hCikg

https://www.youtube.com/watch?v=GhO1OA5RySQ

https://www.youtube.com/watch?v=t7gRTmaLXgY

Jerry

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