Heli_av8tor said:
John - Yes, you should be heavier than me. A thousand on the toad alone. I believe you should have the 6 speed Allison whereas I have the 5 speed. Numerous times I thought having that extra gear with closer ratios would have helped. I too drive 61 / 62 mph.
I ended our trip with 52K miles on the coach. I have good records of maintenance from the original owner but they stop 3-4 years ago. I think it set for several years before I got it. Perhaps illness or death of the original owner?
My manual says the AVG MPG computer gives a 50 mile rolling average. I swear it has to be averaging over a much shorter distance, perhaps 5.0. Normal interstate grades, both up and down, across Nebraska and Iowa just have too much effect on the readout. (Yes, I'm sure it's not in INST mode.) I noticed a strange thing with the mileage computer pulling mountain grades. It would start out at 6 something and decrease to 0.0, then to "---". Then it would go to the 80's or 90's and work it's way back down.
I did try to stick with "Top Tier" gas and started this trip with a double concentration of Chevron Techron fuel additive.
Several suggested that I could have fuel injectors leaking when they are supposed to be closed. I'd like to clean the injectors using something like the OTC Tool ( https://www.amazon.com/gp/product/B00GZ0H9VC/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1 ) But it's pretty pricey for a my limited use.
I won't have another trip until January and it will be across flatter ground. I hope to see a little better mpg, but you're probably right that I'm about where I'm going to be.
Tom
We have the same transmission, most likely. I have the Allison 1000, which is a four gear with overdrive, or 5 gears.
You're lucky you got some records. When I bought my coach, it had 23,005 miles on it and I thought it had been fairly well taken care of because it was a one owner that was former military. But I got no records, had no idea when the last oil change had been done, and didn't know if anything else, such as tranny fluid change, tune up, air filter, etc. had ever been performed due to its low mileage. So I had to spend the money to get it all done whether it was needed or not, just to be on the safe side.
I know exactly what you mean about the rolling average seeming to change drastically quicker than you would think if it was taking a 50 mile average. When I coasted down a mountain this last trip, the computer might have read 6.0 from the climb, but after going downhill only one or two miles, the average was now up to 10.5. Of course, if you have ever switched it to "instant" mode, you have found that when coasting, you'll register in the 20's or 30's. That reminds me of a diesel that consumes no fuel when idling. I never experienced what you mentioned about the reading going to zero or blank and wonder if you may have an issue with your computer, or at least the mileage readout.
I have always used the cheapest gas I can find in all my cars and the coach and have (knock on wood) never had any problems as long as I keep the fuel injectors clean by giving the the required service every 30,000 miles. Now that you mention it, I can't remember if that was done on my coach when they did the tuneup. I'm pretty sure they did.
You can read the many posts from a variety of people who want to make everyone think their coach is better than anyone else's by stating they are getting outrageous mileage. But the simple fact is, nearly every gas coach made is going to get between 6 and 8 mpg. Variances will occur with age of coach because many of the newer ones are built lighter and with more efficient power plants, size and weight will make some difference but not much, whether or not you tow, and the highway, traffic and weather conditions of your trip. One leg of our last journey, I got almost 9mpg because I had a strong tailwind, and one leg, I got 5.5 because I was battling headwinds. That, it itself, in my opinion, gives the greatest variance when driving because when you're traveling in the mountains, the downhills are going to neutralize the uphill climbs to some extent. I actually found myself getting better mileage in the mountains than on flat ground. Reason: I turned the cruise control off and anticipated the climbs by going faster than my norm before hitting the grade. If I was coasting downhill and saw a climb coming up, I would speed up to 68-70 mph so I could make the grade all the way up or most of the way before having to downshift. When you leave the cruise control on, it cannot anticipate those grades coming up and will maintain the same speed all the way down the hill you're on, and then downshift almost as soon as you start the climb. It's a trick I learned as an OTR truck driver. My mileage on flat ground, such as the interstates in Florida, was about 7.0-7.5 on the computer readout, while my mileage in the mountains without the cruise on was over 8.0 most of the time.
Good luck with your mileage. The best thing you can do is simply keep it maintained properly and it will give you its best performance.
