So 5W rotella is synthetic and 15W is conv? You guys are switching back and forth from syn to conv? I have been told it isn't wise to do that, but all of you are pretty experienced so is that just a myth? Or is the 15W a synthetic also?

 

Switching between syn and conv motor oils will do no harm.

 

IMHO - to "avoid" any possibility of "syn shock" as rumoured, run the 15W40 diesel rated oil when you first get the vehicle. The heavy dose of cleaning chemicals get rid of a lot of gunk slowly. Then go to the syn if that works for you. I run the 5W40 now and love it.

BTW, a semi truck pulled over on my road last night with engine trouble. Blown engine. Fleet manager drove out to look at it.

I asked what kind of oil? 15W40 Kendall.
I asked how often is it changed? Every 15,000 miles
I asked how much oil? 10 gallons
I asked what kind of engine? CAT - 400 hp
I asked how many miles? Right at one million
I asked what they would do? Tow it to the shop rebuild entire engine, put another million on it.
What about new trucks? The new emission changes have cut them from some trucks in close to 7 mpg range to 5 mpg. That's on their fleet of 600 trucks.

Different world, and we would all pay a little more for vehicles engineered to actually last longer than the payments. Not what it costs for a semi tractor, but obviously the technology for long life exists - at a price.

 

When I drove truck it was Mobil 15w-40 every 12,000 miles, that was local delivery, local means within a days drive, so 500 miles round trip.
I drove 4 days a week, ~1500 miles in those 4 days.
I put 500,000 miles on one truck alone, original clutch lasted 300,000 miles.
Over the road trucks last so long because it is all highway miles at a constant speed and low rpm.
Semi's at 65mph only run at about 1500rpm, max rpm is around 2500 maybe 3000.
You could always tell when the oil needed changing because she would start using oil, as the oil wore out it would get used.
I would go 10,000 miles without needing any oil, then she would start burning it, 4 qts every 500 miles or so, 4qts is the "add" mark.
In 12 years of driving truck I only broke down twice, once when the clutch went out and once when the fuel line leaked fuel into the crank case and diluted the engine oil with fuel and overfilled the crankcase so much that oil came out of the dipstick tube and the oil was so thin the oil pressure dropped to near zero and leaked past the turbo bearing and she started dumping smoke out the exhaust.
The only other time I was down for a short while I had gelled up on a really really cold morning and I had to change the fuel filter on the side of the highway.

Bottom line, all engines hate being cold, they like being hot and running at a constant speed with a moderate load.
Only drive in the city and shut the engine off and restart it constantly it will not last long, always cruise the highway and change the oil once and awhile and it will last forever.

 

Engine life has improved a lot. I agree with Spike about the highway, but even urban buses have long engine life nowadays. Our gasoline engines have gotten much better too. In the past, a car would go thru one or two overhauls in its life, now the engine outlasts the life of the car in most cases. What is still around is very poor maintenance, and those are the ones that don't make it. Use any oil approved by the manufacturer and go by the manual with the maintenance, and the engine will go for many many miles. On our mining trucks, the life of the engine is measured in gallons of fuel, not miles, not hours. Most of the diesel engines on our equipment are good for 1,000,000 gallons of fuel before overhaul.

 

This man speaks the truth!!

 

If a guy bought a brand new car today, never changed the oil and only kept it full the engine would still last 100,000 miles.
It would be in very very bad shape, it would smoke and rattle but it would still run.

I used to work with a guy who always leased his pick up trucks, usually Toyota's.
4 year lease, he only changed the oil once in the total 4 years, and that was on his way to the dealer to turn it back in after the lease was over.