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distaff · 08-22-2016, 11:29 PM

In March I stopped into a Cat dealer for an oil change (they were right on my route out of town). The tech who did their OTR work saw I had the original flash and suggested a re-flash (I had him check the codes since I'd lost all my coolant a week earlier in San Diego and wanted to see if it had overheated).

After the re-flash I noticed I was going through a lot of fuel, more than I expected given it was a route I drive once or twice a year. Set a trip monitor and it has been pretty consistently 5.6 mpg. Did the same route again in June which confirmed I was burning a lot more diesel.

Since I was at the stage where a valve lash adjustment is due, and I had noticed some performance issues, I decided to do that first. The valves were loose, and they are now in spec, and I noticed on this trip (again, same route) we got about 6.1 mpg and it is pulling stronger.

Now I know the engine is running optimally I need to go back to Cat and ask what is going on. I do know I had the original factory flash on the ECU, and it may not be relevant but it took the tech 6 tries to get it to accept the new flash (he eventually bypassed the Monaco wiring and went to the ECU directly, but even that took two cracks).

I also know the new flash is one that is intended to reduce NOx emissions by changing the timing of fuel injection. I have been told by Cat that the 3xxxxxx flash numbers are all NOx releases, and the ones that start with a 2 (as did my original flash) are different.

Anyone else have a significant loss of mileage after a re-flash?

slemnah · 08-23-2016, 06:53 AM

I assume that you have the C13 engine in yours? I have been fighting crappy fuel mileage since I bought mine and it has been re-flashed a few times in its life. I average around 5.4 with mine, less if I pull my trailer. One thing that the reflash does is override a program that would fry the ecm. I don't remember the details but I know that it would cook the ecm and leave you stranded. I would love to know if you find a way to get your mpg back.
Steve

distaff · 08-23-2016, 11:22 PM

I do have a C13. Until this year I loved it! Will post my progress.

slemnah · 08-24-2016, 07:03 PM

I would love to know if you find the magic bullet to get mpg back

krivanj · 08-24-2016, 08:26 PM

I have a C9 but two years ago I went in to a Cat dealer as I had a bad sensor. After that was replaced, I asked about a reflash. He said he did not recommend one as they usually are only to reduce emissions and reduce mileage. I passed.

sevenmacs · 08-24-2016, 10:06 PM

The first year of owning my Cat C7 MH I had it reflashed due to a hesitation issue. I was consistently getting high 8's for mileage . Since flash rarely do I see 8's, usually low 7's. Also has valves adjusted.

jnwhite · 08-30-2016, 11:05 AM

Thanks for the C7 comment. I got a 2007 C7 that has never been flashed. Cat RV Hotline says there have been a dozen flash updates since then. Some emissions, some performance. First trip since purchase will be soon. Will check mileage. If in the 8's, I think I will leave it alone.

Jay

distaff · 09-04-2016, 04:07 PM

Shifting back to my C13 - I spoke to the CAT RV hotline on Thursday and was told that CAT would NOT make an old flash available and the guy wanted to know what CAT tech had said they would.

I am now going to consider either an aftermarket flash or a custom one.

mchero · 09-09-2016, 08:46 PM

Thanks for the post & please keep us posted. I have the C7 & avg.about 7 to 8 so I'll NOT go the flash route! LOL

distaff · 11-29-2016, 10:57 AM

Just an update - I decided not to do the re-flash this year. I'm going to put some miles on it and track the mileage. I may re-consider when I see the numbers.

mchero · 11-29-2016, 10:59 AM

Thanks for the update Paul. I'm not going to touch my CAT. Don't think a flash will do me any good. 30K on her & she still purrs like a kitten!

tropical36 · 11-30-2016, 09:18 AM

Quote:

Originally Posted by mchero

Thanks for the update Paul. I'm not going to touch my CAT. Don't think a flash will do me any good. 30K on her & she still purrs like a kitten!

I'm scared to let anyone touch mine and at about 38K miles by now, it's never been touched, according to CAT. Mileage isn't all that great and not even sure how, many on here, are even calculating it, but I'm going by the on board computer readout. If we're running on the level, it consistently says it's getting in the mid 7's, which I feel is acceptable with that much weight and pulling over two tons of toad. Thing is, if you look at total average, which could be over it's 9yr life, for all I know, it's a consistent 6.1. Then, if you consider all the traffic stops, shifting and idling, it's probably right on.
Did I say that we normally drive with the speed control between 55 - 57mph and since it will stay in 6th gear at that speed. Even over some hills, in fact.
Going any faster than that means that we're in a hurry and that's not what we bought an RV for. Others may choose another lane if they wish and do what they can to raise fuel prices, but that's not us and again your mileage might vary. As long as there's nothing wrong with the rig, I don't even consider fuel all that significant with the cost of ownership, anyway.

distaff · 12-03-2016, 03:18 PM

Quote:

Originally Posted by tropical36

I'm scared to let anyone touch mine and at about 38K miles by now, it's never been touched, according to CAT. Mileage isn't all that great and not even sure how, many on here, are even calculating it, but I'm going by the on board computer readout. If we're running on the level, it consistently says it's getting in the mid 7's, which I feel is acceptable with that much weight and pulling over two tons of toad. Thing is, if you look at total average, which could be over it's 9yr life, for all I know, it's a consistent 6.1. Then, if you consider all the traffic stops, shifting and idling, it's probably right on.
Did I say that we normally drive with the speed control between 55 - 57mph and since it will stay in 6th gear at that speed. Even over some hills, in fact.
Going any faster than that means that we're in a hurry and that's not what we bought an RV for. Others may choose another lane if they wish and do what they can to raise fuel prices, but that's not us and again your mileage might vary. As long as there's nothing wrong with the rig, I don't even consider fuel all that significant with the cost of ownership, anyway.

Not sure I am with you on the 57 mph thing, we tear down the road at 60-62.

Based on my experience I would not put a newer CAT flash on my machine again. I may get a custom flash at some point. I was considering an older European flash, but it would back the HP down to 500 hp and I don't think I want that. I'll track my fuel use on my next trip and then decide.