Mileage

[JDT]

Diplomat Don's post about his fuel guage problem got me to thinking. He said he got better mileage going 65 mph on his last trip than he did going slower on other trips.

I have kept a log book on mileage since we bought the coach 4 years ago. We are approaching 20K miles on our 05 Ambassador with a 330 Cummins. Whenever we take long trips with our traveling friends, one of them has a fifth wheel and a lead foot. I have generally run 58 to 60 mph when traveling by ourselves, but agree to do 64 when with the group. I have a great excuse as our 4700 pound Acadia has a 65 mph towing limit. Our last trip was 1900 miles and I averaged 8.5 mpg. I looked at some trips that I knew were taken at slower speeds and mileage was about the same or sometimes less. Some of these were towing a much lighter PT Cruiser as we bought the Acadia in February 08. Also, we just got back from Branson (420 mile round trip) which I did at 64 mph. I looked at some of our previous Branson trips which I knew I did at slower speeds and the mileage again was about the same.

I am about to decide that going slower has no benefit, other than maybe a safety factor, which is very important to me. Wondering who else has experienced this.

Also, I have no way to keep track of this other than the old fashioned way. I always try to fill the tank to same spot but I'm sure it varies on occasion. I see many of you have something you call Alladin, Jr. and maybe something called VCM. Are there any benefits to having this, other than mileage tracking, and would one work on my coach?

Jim

[twalton]

Hi Jim,

My opinion only, but I think you hit the nail on the head when you said that the priority is to choose to drive at a safe speed. Personally I've given up monitoring fuel consumption other than when the guage gets close to empty, I stop and fill up. As for monitoring devices for your coach, ScanGuage II at about $160 is easy to install and will tell you more about the operating conditions of your engine and transmission than you have time for if your driving.

[rex]

The Scan Gauge will not work on a diesel engine, but does fine on a gas one. For the diesel you will need a SilverLeaf and their free software VMSpc. Their device will connect to the engine diagnostic connector under the dash of most diesels.

[Dutch Star Don]

JDT.....You and others may think I'm nuts, but we also found the coach pull harder and the hills at 65. We're on our last leg of our trip to Yellowstone and will be home tomorrow. We took I-15 up and back. There are a lot of grades both big and small. Only two dropped me to 60 when I hit them at 65. We're towing my 07 Dakota (4700 pounds). At 65, I'm running right at 1700 RPM which is my peak performance.

[AFChap]

I don't have a Monaco, but this isn't just a Monaco thing. I have a 40' coach with 350hp Cummins ISC and Allison 6-speed tranny. In flat country, I generally run between 60 & 65 (my 6 speed tranny normally does not stay in 6th gear unless my speed stays a little over 60). I have noticed that when I am driving mountains the coach does noticeably better if I am running a little over 65 as when I hit an incline it downshifts at higher RPM and is able to maintain a higher RMP/better speed up the hill. Higher cruising speed minimizes engine lugging, and helps mileage when doing lots of climbing.

[Dutch Star Don]

We just got back from dinner and I pulled out my mileage book. We've done almost 3000 miles in the last three weeks. I never trust any one fill up because my coach can take almost 10 gallons more if it's not on level ground. Over the 3000 mile trip and 7 fillups, we've averaged 8.9 mpg towing.

Normally, we've been averaging 8.1 - 8.5 (not towing) at 60-62mph.

The only reason we've been driving faster was that we were unable to make several trips because of an injury and we decided to make some fast trips. The price of fuel is also cheaper now than when we bought the coach new.

[cb5300]

People kept calling me crazy when I said the same thing that you're saying now. On my coach, at MPH I get 4.0 mpg, at 69 mph I get 6.4 mpg. I spoke with the Cummins guy about this, and he told me (after dyno pulls) that with my coaches gearing ratio my "sweet spot" was 1600 rpm, which happens to be 69 mph. I also find that I enjoy motoring along with the flow of traffic instead of causing traffic back ups...

[Jim Stewart]

The VMS Silverleaf is a great tool. When set up, it can give you load (HP), torque and instantaneous MPG. This is actual information taken from your engine. It actually uses the load and torque to calculate MPG.

I have seen mine at different speeds and with and without the Toad. Same speed with the Toad requires more HP than without the Toad. I also can see that greater speed requires more HP. Each Coach/Engine combination will have a sweet spot where you achieve the lowest load and greatest torque at a specific cruising speed.

In almost all cases, lower cruising speed within reason (if you do not get in your top gear you do not acheive the sweet spot) will mean greater MPG! The question is how much and is the difference in $ worth your time.

[JDT]

We are taking another 1800 mile trip with our RV friends next month so get to go 64 mph again. This time we head to Colorado so will have some limited mountain driving since we are only going to Woodland Park, west of Colorado Springs, for a week or so and then down to Albuquerque for the balloon festival. We'll be coming in from the east so the major climb will be the short trip from Colorado Springs up to Woodland Park. I always try to get up speed before hitting a steep grade.

Jim Stewart, I am very interested in the VMSpc by Silverleaf. In fact, I'm think I'm going to order one of the small netbook computers, like the Aspire One, to run it on. The wife has a Sony VIAO but she won't let me use it for that as it might conflict with when she wants it. I've wanted my own laptop for a while anyway so this gives me a good excuse. I called Silverleaf and they said the system will work fine on the small netbooks. Any suggestions on the VSMpc's usefulness? I admit I am kind of a gadget guy that likes to know probably more than I need to about how my engine is doing. Also, any suggestions on where to buy the system? About the only place I have found it is RVUpgrades.com.

Jim

[Sixpack98]

Originally Posted by Diplomat Don

We just got back from dinner and I pulled out my mileage book. We've done almost 3000 miles in the last three weeks. I never trust any one fill up because my coach can take almost 10 gallons more if it's not on level ground. Over the 3000 mile trip and 7 fillups, we've averaged 8.9 mpg towing.

Don,
On our last trip, which was about 3200 miles we also averaged 8.9 mpg over the 3200 miles towing a Tacoma PU. This is the best we have ever gotten over the 22000 miles on the coach. In our case I think there are a couple of factors contributing to the better fuel mileage. I think I manage the rpm much better now and try to keep it in the "sweet spot" when approaching a grade and don't let the engine lug. I also tend to drive a little faster now, from about 62 to 65 or so. Maybe the biggest factor is the engine is just getting broken in.
We're leaving soon for a 2000 mile trip and maybe I can break 9.0 mpg over the 2k miles.

[Dutch Star Don]

Sixpack98.....I think you're right about paying closer attention to the "sweet spot". One of the problems that we have is that we take a lot of short trips with an occasional 1000 miler. When we take these longer trips (3400 miles in 3 weeks) you really get to learn more about the coach. By the time we take another long trip I have to learn everything all over again.

Ours hit the 30000 mile mark this trip and is running great. I know a lot of people don't believe in additives, but I use "Opti-Lube XPD" and I think it helps.

[Mbl Cndo]

Originally Posted by Sixpack98

Don,
On our last trip, which was about 3200 miles we also averaged 8.9 mpg over the 3200 miles towing a Tacoma PU. This is the best we have ever gotten over the 22000 miles on the coach. In our case I think there are a couple of factors contributing to the better fuel mileage. I think I manage the rpm much better now and try to keep it in the "sweet spot" when approaching a grade and don't let the engine lug. I also tend to drive a little faster now, from about 62 to 65 or so. Maybe the biggest factor is the engine is just getting broken in.
We're leaving soon for a 2000 mile trip and maybe I can break 9.0 mpg over the 2k miles.

I guess I must be doing something wrong here... we tow a 3100 pound Saturn and am averaging 2 mpg less than the both of you on relatively level ground.

[Jim Stewart]

Originally Posted by JDT

We are taking another 1800 mile trip with our RV friends next month so get to go 64 mph again. This time we head to Colorado so will have some limited mountain driving since we are only going to Woodland Park, west of Colorado Springs, for a week or so and then down to Albuquerque for the balloon festival. We'll be coming in from the east so the major climb will be the short trip from Colorado Springs up to Woodland Park. I always try to get up speed before hitting a steep grade.

Jim Stewart, I am very interested in the VMSpc by Silverleaf. In fact, I'm think I'm going to order one of the small netbook computers, like the Aspire One, to run it on. The wife has a Sony VIAO but she won't let me use it for that as it might conflict with when she wants it. I've wanted my own laptop for a while anyway so this gives me a good excuse. I called Silverleaf and they said the system will work fine on the small netbooks. Any suggestions on the VSMpc's usefulness? I admit I am kind of a gadget guy that likes to know probably more than I need to about how my engine is doing. Also, any suggestions on where to buy the system? About the only place I have found it is RVUpgrades.com.

Jim

JDT,

I bought the "box & cable" used on the internet. You may want to do a search, the cable is vehicle specific but I believe there are only 2 or 3 different types (pin fits your socket). I run it on my Samsung N120 Netbook.

I would recommend the new HP Netbooks that are $329.00 or less (non-glare screen). RV Upgrades is the least expensive for a new unit that I have seen, but again, do a search.

The unit is easy to set-up and after you play with it for a while you get the hang of it. You can go onto the VMS Website and download a free copy of the software and play with it to see what you think.

Jim

[Sixpack98]

Originally Posted by Mbl Cndo

I guess I must be doing something wrong here... we tow a 3100 pound Saturn and am averaging 2 mpg less than the both of you on relatively level ground.

I don't think we have ever averaged 6.9 mpg, even when towing in the mountains of New Mexico, Utah or northern Arizona. When our coach was new it averaged somewhere about mid 7 or so. It gradually crept up to around low 8 mpg and slowly crept up from there to about 8.5. Our last trip was pretty flat except in West Virginia and SE Tenn. Probably somewhat subjective and maybe anecdotal but I believe we get better fuel economy towing our Tacoma which may be breaking up the drag on the back of the coach. We take several short trips a year to the Texas coast and some of the times we don't tow. We can generally make these trips on a tank of fuel and I always fill up about a mile from where we store the MH so I think the tank fill error is about the same each fill up.