Originally Posted By: Ken2
etex, there is almost nothing you an do that will pay for itself. One thing--the oversized tires make fewer revolutions than the stock tire size, so you're odometer is registering fewer miles than you actually travel--that makes your miles per gallon calculation look lower than it actually is.
Because you're shopping for new tires, there are a couple of low rolling resistance tires that will be a small benefit. (Do you need new tires, or are you buying tires to save gas...if so, they probably won't pay for themselves in the gas saved, if any.) Michelin LTX M/S2 and General Grabber HTS claim to be LRR. There may be others. LRR resistance is a marketing title by the tire makers--they may save some gas, but no telling how much.
How tall is your trailer? That windage is a big consideration. The air defectors on top the cab are another gizmo that don't pay for themselves.
Air Tabs are another fuel saver that likely won't pay for themselves with your low mileage. Ditto exhaust upgrades...long tube headers might help, but won't pay off. Intake changes, if they do any good, at best do half the good of exhaust changes, and won't pay off.
Your choice of engine oil won't make enough difference to buy a cup of coffee. The only things you can do that will work are to slow down and carry as little weight as possible. Don't even think of upgrading to a diesel until this truck dies. You said it well--gas costs less than truck payments. When it is time to get a different truck, do you really need the dually to tow 13,000#? If a one-ton single rear wheel truck will carry that trailer hitch weight safely, go with the single.
According to the speed displayed on my GPS, the speed displayed on the speedometer is actually very close to correct. I can only assume that when I return to the "correct" size tires, the speed displayed on the speedometer will actually be a little high. I've always heard that the automakers make the speedometers a little faster than the actual speed, but I am not sure why. According to the tire size calculators on various websites, the difference in speed in these two tire sizes at 65 mph is about 2.5 mph.
Because this truck sees so few miles, new tires are not a good buy. I rot them off long before I wear them out. The tires that are coming off the rear of the truck now are Continental Vanco Four Season. I am taking them off the because the tread depth is near zero. I picked them up used a couple of years ago. The tires I am putting on it are Goodyear Wrangler SR-A. I picked up the four of them a few weeks ago for a hundred bucks. I hope to get two years out of them. Finding good used 16 inch truck tires with date codes less than four years old is getting very hard to do. Four new tires for the back of this truck is $600 from tirebuyer.com. If I ever do get new ones, they will probably be Firestone Transforce HT. I've got a set of those on my half ton truck, and I love them.
The trailer is 38.5 feet long and I guess about 12 feet high. It punches a huge hole in the air. That extra wind drag is probably hurting more than the extra 4000 pounds I gained when switching to this trailer from our previous bumper pull trailer.
I talked to the local exhaust guy earlier in the week about how much would be helped by replacing the exhaust from the muffler back. This truck is a true dual exhaust system back through the cats to the muffler, then both pipes go into a huge muffler, and there is one tail pipe coming out. We decided it would be a waste of money. The muffler is huge, so any restriction there would be minimal. Headers have never even been a consideration. I don't want to get into stuff like that. After messing with headers on my race cars for years, I understand that they require constant attention, and they live very short lives.
I've decided to stick with the 15w40. I may make it synthetic if the price is right. If not, then I'll just stick with the conventional oil.
I'll play around with the slower speeds on my next trip. On a 300 mile trip, going 55 mph instead of 65 mph will add 45 minutes to the travel time. That's not a big deal. I need to learn to be a little more patient.
This truck has been very good to me. From the moment we bought it in 2000, it hauled my race car all over the states of Texas, Oklahoma, and Louisiana, until I retired from racing a couple of years ago. It's never laid down on me. The most major items I've ever had to replace on it are the water pump and the hydraboost unit. I'm getting ready to do some air conditioning work because of leaks. That's where it's nice to have my wife working at a dealership. I'll buy the parts and let her service department do the work. I don't enjoy working on cars near like I used to. That's one of the reasons I quit racing. Maybe I'm just getting old.
Thanks to everyone for the replies in this thread. I've learned a few things. I had read some wild claims on the internet about gas mileage improvement after changing to synthetic oil. I wanted to throw the question out there and see what everybody had to say.