Cat 3126E vs. Cat C7 vs. Cat C12

I would give the C12 a great reference also. In our case it is mated to a very light weight coach and the mpg's are outstanding. Lifetime mpg is 9.4. Yearly service @ Speedco is only about $200.

bluwtr49 wrote:
The C-12 is a great engine and also quite fuel efficient IMHO. We avg 8.5 and that is the average since the engine was born. . . .

Thanks! That's very reassuring. The C12 I'm considering is in the 1999 motorhome, also 40', so I suppose it is a pre-EPA-changes C12, which may help the mileage.

I've done a lot of Googleing on this and have found a lot of comments that the C12 is a very "thirsty" engine. Maybe those have been mostly later models with the changes to meet EPA requirements for emissions, which have hurt fuel economy.

From among the motorhomes we're considering, it's a close judgement call. The cost of operation, including the cost of keeping it fueled, will be a big factor in the final choice.

Wayne

The C-12 is a great engine and also quite fuel efficient IMHO. We avg 8.5 and that is the average since the engine was born. Lot's of HP, gobs of torque and hasn't drunk a drop of oil.

Tough to ask for more from a big diesel.

As already posted, none of the engines he is looking at are ACERT which started with engine (not coach) production as of 1/1/2004.

3126E and C7 are basically the same basic engine.

The C12 which would be paired with an Allison 4000 vs 3000 for the 3126/C7 will be found in larger, heavier coaches.

If you have a specific coach in mind, call the Caterpillar RV Hotline with the engine serial number: 877 777-3126

Brett Wolfe (wolfe10) is our resident CAT expert. Send him a private msg and I'm sure he can answer all your questions.

Motorhome engines are based upon the weight of the motorhome. The heavier the motorhome, the bigger the engine. It's all about the weight/torque ratio. My coach is about 25000 lbs and my C7 has 860 lbs of torque....so my ratio is about 30:1. So, when you check other motorhomes, do this quick math problem and it will provide you with which has the better ratio. Some mfg's will put the same engine in the same model coach regardless of its length. The longer models will then get poorer mpg than the shorter ones, and have less power on acceleration and hill climbing.

The C7 is an upgraded 3126 so there probably won't be much difference in problems, maintenance, and mpg. Obviously, the C12 will be much more in maintenance and probably less in mpg.

Ron

I had a 3126 in my last MH and liked it very much. Now have a 400 Cummins and I think the biggest difference is 8-9 MPG in the Cat and 7 with the Cummins. Go up the hills about the same just went up them in a lower gear with the Cat and a higher gear with the Cummins. Cannot speak to the C12. My understanding is the Cat C7 is a newer model and is what replaced the 3126 so my simple mind said they were about the same.

Model years are between 1999 and 2004, so I don't think exotic pollution controls will be an issue, except perhaps on the first generation C7.

I'm really as much interested in a comparison of the different engines, especially as regards to:

1) known problems which will become repair costs,

2) cost of maintenance (for example, I've found that the C12 takes about twice the oil for a change compared to the 3126/C7 – I assume other fluids are comparable,) and

3) cost of fuel (driven not too aggressively, is the larger C12 going to use a lot more fuel than the smaller engines?)

Wayne

Ivylog wrote:
Do a google search on CAT ACERT engine problems and then decide if you want a C7 or a C12.

If you do some reading, you will find the failures started when they introduced EPA emissions in the 07 engines. Most of the ACERT failures and lawsuits involve C13 and up engines, basically those with Clean Gas Recirculation, Twin turbos, and the CAT Regenerative System (particulate trap). A C7 does not have twin turbo's, CGR, or the Regen System. I don't know if the C12 has any of those systems on them or not.

Do a google search on CAT ACERT engine problems and then decide if you want a C7 or a C12.

My 3126E has served me very well, and my chassis has been bullet proof. I have it service as per the manual. Never felt under powered, and does just fine on mountain roads, I'm never in a hurry to get anywhere. I have gotten 9-10 mpg at 55-60 mph regularly.