There is much to be said for using synthetics throughout the entire vehicle. But, as has been stated, the real world and real situational conditions may not trend that way. Individuals that keep a single or small fleet of trucks for longer periods will be open to such a change, but the larger fleets that have 3 year turnovers and contract deals with OEM's will not change their ways. And why should they? They can use a minimum recommendation for oil per the OEM and then dump the truck back onto the OEM at a contract period of mileage and move on to the next truck. Their biggest problem is keeping drivers from destroying perfectly fine trucks before the trade time. I, as a smaller truck operation owner, do see the benefits of synthetics and use full and blends as I see fit and cost benefit analysis plays out. I do take issue with testing relying only on dyno results. There are just plain too many variables pulling various loads thru various ambient temps, terrains, and such that can skew any results one may see on a dyno. I have only found dyno testing to be a good analysis of engine condition.
The OP dealt with fleets using synthetics. I think we can see that a vast majority of large fleets are not going to "break the mold" and go that route. Take that fact and add to it that, in this economy, the larger trucking operations are gaining ground on market share and either driving out the smaller carriers thru rate competition or buying them up. It is a real cut throat realm in transportation these days. To expect much change in standard lubrication practices is bordering on fantasy land.
Synthetics, for some time, will stay a niche market share. A large fleet can actually save more fuel by converting from dual drive axles to a drive axle and a pusher axle. They can carry more cargo due to reduced weight, the initial cost of purchase is reduced, and there is better fuel mileage out of decreased rolling resistence by not having to turn a whole set of additional gearing in the second axle. Better fuel mileage at reduced cost. That is what it takes to break down the wall at a large fleet maintenance shop. Even then, only a very small percentage of fleets are even considering this kind of change. Mesilla Valley Transport is the only moderate sized carrier that has even moved in this direction, even though it is quite common in European fleets.
Doug, your break even point actually supports my contentions here. A lot of American larger fleets are dumping their trucks back onto the OEM's at or before that interval. Your example of 4 year equipment retention is not standard for U.S. large fleets. A typical turnover here is 2.5 - 3 years. Now, the typical single truck or very small fleet owner will hold onto a truck for several years to near or over 1 million miles. That is the target audience for synthetics. Regarding holding down the idle time, the individual owner will do that automatically to reduce his cost. The larger fleets have more difficulty in that area as "company" driver attitudes usually do not reflect such a concern for fuel mileage. And we all know, the largest increase in fuel mileage is a direct result of operation of the vehicle. No micro managing by those in the office will have near as big of impact. You can "chastise" all the drivers you want, but you still need to fill the seat. And most company drivers only understand floor the accelerator and then stomp on the brakes. All this because most fleets don't implement any meaningful incentive for drivers to do better. And we all know that you can attract more flies with honey than with vinegar.
I would be surprised to see a deletion of the overhead done on your fleet as well. It isn't only the valve train that is adjusted, as injectors are also checked and adjusted. This procedure can keep a particular engine operating at peak effeciency. Also doing a pressure test of the charge air cooler would be a recommended practice, at a minimum, annually. Just the CAC leaking can equate to 10% loss in fuel mileage. And, how many actually know what the rolling resistence of their tires are? I do. It is a good portion of my tire purchasing decision. Or what of low restriction straight thru exhaust mufflers? All of which do not increase costs (or only so slightly) and decrease fuel usage. Synthetics may reduce fuel usage, but not at the same cost benefit ratio as the other options I have mentioned, hence, the apathy of larger fleets switching over.
