My husband and I drive a 1986 Chevy G-30 one ton diesel " truck" (actually a used short school bus). Not sure of the mileage because it only goes to the 10 thousand mark, not the hundred thousand. Engine is a 6.2 liter. We've had a number of problems with it since we got it because we spent 3 1/2 months driving it 9,000 miles across the country, so lots of wear and tear in a short time (feb through may). Also, although this may not be relevant, it has a second fuel system so it runs on used vegetable oil. No engine modifications, just a second set of fuel lines running from the veg tank with heaters, and switches to switch from diesel to vegetable oil and back.
A few times we've noticed a little bit of smoke and a burning oil smell coming from under the hood after we drive. Never major, though. But it happened again yesterday (my husband changed the oil last week and it hasn't been driven much) and when we pulled out the dipstick to check the oil level, smoke was coming out of the dipstick tube. The level was a little low, so he added a quart, and smoke was also coming out of the hole where you add oil. Can't seem to find a leak anywhere, and it's worrisome that the oil is so hot inside the engine that it's burning off.
The second problem that might be related is when we're driving, the engine hesitates sometimes while you accelerate. Then it will surge again. This has been happening for a while, but we do so little driving now that we haven't had it checked out.