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Old 07-11-2014, 03:19 PM
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JimFreeh JimFreeh is offline
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Join Date: Mar 2007
Location: Hampton Roads, Virginia
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Quote:
Originally Posted by TimFreeh View Post
double

Want to see 44-46 MPG from a CDI? I'm almost 100% sure anyone can if they drive it a constant 50MPH on a flat road with no headwinds on a nice day with the tires inflated to 40PSI and the A/C off. I'm also betting you could get 38 MPG out of an OM603/W124 combo under the same conditions.

Nobody here ever stated you could get 46MPG on a daily basis under normal driving circumstances. The data you reported from fuelly sounds about right for someone that is driving primarily in a suburban environment - and its what I'd expect to get if I was driving in such an environment.

The expanding hot diesel thing is certainly a real issue, however that is only an issue if your re-filling from a tank that is fairly full - if you're checking mileage after the reserve light has come on and you've got 1.5 gallons of 'hot' fuel in a 21.5 gallon tank I don't see it as a significant factor.

It's insignificant.

The standard reference temp for fuel looks to be 60 degrees F. If you use 100 degrees F as your ratio, the difference is 1.84%

Now, since you are filling up a tank that's much less than full, the real affect is about 5% of the above number. That would be less than 0.46%

Now let's assume the ambient temp wasn't 100 degrees F (Hint: It wasn't.). How about halfway between 60 and 100? So now we're looking at an a possible effect of less than 1/4%.

BTW, my father had a Chem E. PhD. I'm well aware of the temperature bias WRT when to fill a vehicle. Dad always encouraged us to fill up in the morning. That habit, is one of the many legacies he left.

Jim
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