Hello all,
I am a civil engineer for South Carolina's DOT and was told to bring my truck (Ford Ranger 3 liter) over to the maintenance shop for an oil change this morning. Since I was the fist in line for the day and they were only doing a oil change I stood there and watched them do it. They put it on the lift, drained the oil, replaced the filter, and rolled a 55 gal drum of oil over to refill the truck after lowering it. Much to my surprise, the oil drum was full of Citguard 500 15W40, CI-4 rated by the way. I asked him if they put this in all DOT vehicles. "Yep, everything for as long as I can remember" he said. He will be retiring later this year. Everything is Rangers, S-10's, Cherokee's, full size trucks - 6's, 8's, diesels, Suburbans, Blazers, Tahoe's, Taurus', heavy dumptrucks, backhoes, loaders, grade-alls, etc.
I'd be willing to bet that the diesel trucks are the only one's that spec this oil. State vehicles (light trucks and cars anyway, are kept to 125,000 miles and serviced on 6 month 5,000 mile intervals. This is not high miles but most vehicles are 10-15 years old when they are turned in. They are operated off-road, in dusty conditions, abused, thrashed, basically treated like rentals for these 10-15 years. I can say in my 9 years here that the engines are about the only things that don't require a lot of repair or replacement. Most of the light trucks will be on their 2nd or 3rd tranny and rear end by then, but the engines rarely use oil, smoke, or require overhaul.
I'll leave it to you guys to draw conclusions. Personaly, I buy a new car every four years and do what the owner's manual says.
Best regards,
Patrick