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metro-mike

Rpm, Gear Choice And Mileage

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I have a 2005 Cdi that I bought a couple of months ago with approx. 94,000 klm. On my first tank I got approx. 68 mpg and thought I could have done better, but since I was new to driving a diesel, I figured I was reving the motor to high. So the next tank I tried to monitor the rpm closer to make sure I kept the rpm at a lower range, under 2500rpm. That tank was close to 65mpg. So I bought a X-guage to watch what I was doing and the next tank I tried to keep the rpm under 2200rpm, my mileage was 61!! Most of my driving is on a freeway with the speed is around 60mph, 100klm. Well yesterday I noticed than when I'm in 5th gear at around 3000 at 100klm I was getting close to 65-70 mpg but when I dropped in to 6th gear the mileage dropped to the 50's. So I kept the car in 5th the rest of the way home and the mileage was keeping in the upper 60's and the low 70's. The only thing I noticed was that the water temp went from 172 to staying at 180-185. Any ideas why my mileage drops so much when I drive in 6th gear? I know that when I'm close to 3000rpm that the turbo is running high and squeezing more air into the motor, but I'm at a loss to figure out why my mileage is off. Sorry for the long post, just wanted to give as much information as possible. Thanks...................

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That is very unusual behaviour, my two smarts both drink a lot more diesel in 5th than 6th.Don't be shy, take the car to 3K RPM and beyond when accelerating and don't put it in 6th below 90 km/h on a flat road.Your car may be down on power since it won't happily pull 6th.....do you get downshift arrows when the FE gets worse in 6th?

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Ambient temperature has a huge role in mileage. I had my first 500km tank this week, daytime highs @15-20C. My short 20km commute won't even bring it to operating temperature when it's below -10C, then I get @400km per tank. It can be tricky to use an X-gauge to monitor fuel consumption. The best way is to record mileage after every fill-up to find out the true fuel economy, then compare it to the numbers your getting from the X-gauge. A great online resource for storing this info is http://www.spritmonitor.de/en/

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I was trying this last night, and I think there is something seriously wrong with your X-gauge settings. Cruising along in 6th on a level road, and I was using around 4.0 L/100km, shifted to 5th, and it would stay steady around 5.5 or 6.0 L/100km. I would be checking your measurment devices first.

Edited by MightyMouseTech

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I have a Welt-engineering x-guage. I going to borrow a friends scan guage this weekend, and use it next week and see what my results are. The air temp has been fairly consistent.

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Well after using a Scan guage for a couple of days, it is pretty obvious that there is a problem with my Welte x-guage, when it shifts into 6th gear. When I drive with the scan guage in 5th and upshift to 6th, mpg goes up pretty quickly. Thanks everyone for your input.......... Next step, Remap......

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