Oil for a DD 6-71 Turbo

[sdan27]

We resurrected this old 1980 OshKosh truck that's been basically just sitting around our farm for the last 4 or 5 years. I think it has a Detroit 6-71 engine but I'm not sure because the tag is missing. It is an inline six. Before we start using it, I was going to do an oil change. I know that the 2-strokes like mono-grade oil so I was wondering, with an engine that size, if I should use 30 weight or 40 weight oil. It will be used almost exclusively in the spring/summer/fall months so it won't be super cold. Even after all that sitting, once we got the battery charged up, it only cranked about twice and it fired right up. No ether even on a balmy 30 deg F day and earlier this week it had been in the teens mostly.

 

[Steve S]

Straight 40 and I think a DELO 100 or equivelent may be the best choice. I remember driving a semi truck that had a 6-71 non turbo takling about low power!! good thing the company paid by the hour. You must have a really big farm!!! I couldn't imagine what it takes to work the place. Detroits usually start pretty easy compared to the Cummins of the day.

 

[nthach]

Use a single-weight API CD/CF oil. Wal-Mart carries monograde Shell Rotella.

 

[Chris142]

Yup SAE40. No 15w40 or any other multigrades in this one.

 

[sdan27]

We bought the truck from this local cement company for like 5 grand I think. When my dad bought the truck, it was before I was working on the farm full time, they did an oil change but I'm pretty sure they didn't know any better and used 15w40. Its already fitted with a bypass oil filter so how many hour do you think I could go on an oil change?

 

[rslifkin]

Straight 40 (CF-2 rated) is the right stuff, maybe a straight 30 in very cold weather.

Make sure the airbox emergency slam door works and seals properly, and that the turbo seals are in good shape. If one of those starts sucking oil, the resulting runaway can be pretty ugly.

 

[Ken2]

Lots of those engines have run with all types of oil, but the CF-2 spec oil is the right stuff for longest engine life. As said above, 40 wt in the warm weather.

Do check the correct operation of the emergency shut down flap under the supercharger. I've had one that didn't shut quite tightly and had to stop the engine by discharging a CO2 extinguisher into the air intake. If the supercharger shaft seals leak too much oil into the air, it'll run on the lube oil even after you shut off the fuel, and run until it grinds itself to a stop from no oil.

A strong engine, light weight for the power, cheap to buy and cheap to repair, uses relatively lots of fuel and lube oil. Normal oil change interval is about 150 hours.

 

[rslifkin]

Ken - That's a description of a pleasant runaway. If it's still getting too much air, it'll rip the blower seals apart, suck oil faster, over-rev and blow itself to pieces.

 

[sdan27]

The band clamp on the turbo, between the intake side and the center section was still on there but it was not clamping as the bolt was sheared. I took it off and there was a pretty fair amount of oil on the bottom side so I figure the turbo seals are already leaking some. I think I will try and take it off and see how much it costs to have repaired and if it seems too much I might just try and run it without the turbo. The truck has like 260,000 miles but also has like 9100 hours so its probably due.