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Hello,

I replaced the engine in my 2004 EM2 (Car has 98000mi) about 1000 miles ago with a 45000mi engine from japanengines.com. After the replacement, I switched from Vons gas to Chevron, and right after we got it running again, I ran some Techron fuel system cleaner through. Before the replacement, I had gotten 40-42mpg on a 200+mi stretch of highway multiple times, but since replacing the engine with the same one (d17a2), I made the same trip, and only got about 36. Anyone have an idea as to why?

 
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more than likely your old engine was in better internal condition. after about 20k miles, the engine should be getting its optimal mpg already. try some auto-rx.com in the oil.

 
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This has happened to me too. Well, on the same car with same engine. I used to get up to 44 mpg on my long hwy drives to L.A. Lately, my fuel mileage has been sucking *****. In the past 2 years, it has gone down to 34 mpg. I don't know what's up.

 
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so many things that could be the cause...

 
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Personnally I am happy with anything north of 30 most days. 36? Nice, the 40s seem like a pipe dream to me with this car. Might be better with a manual, not an auto like I have though. Even then it may be a only be a couple better. The stars have to align to get anywhere over 35, and pokey is the name of the game. If I run slow enough to get stellar mpgs I will get ran over daily....

 
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just going from summer to winter will drop about 10mpg on the highway.

 
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I don't think so. My commute is almost completely highway and I see a difference of between 3 and 4 mpg between summer and winter.

 
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well i am talking about going from 95F to around 0F. it did for my car anyway. i get around 42mpg summer and 32mpg winter going 60mph all highway. every car is different i guess.

 
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Drop in highway MPG......over a couple years?

Different tires? Tires can make a big difference in economy. Softer tires with a more comfortable ride seem to get lower gas mileage sometimes.

Tires, tire pressures, and fuel would seem like the most likely major factors to me.

Oxygenated fuels net lower gas mileage, Ethanol is the same thing.
I'm thinking this is nationwide, now that MTBE use has been banned.




Googled: oxygenated fuel mpg
Also google: RFG (reformulated gasoline)



http://artsautomotive.com/publicatio...-mileage-story
#2 An explanation of oxygenated fuel's effect on mileage
Beginning in October or November, gas companies at an oxygenate to the fuel to decrease tailpipe emissions. The oxygenate additives, unlike hydrocarbons (gasoline), do not store energy, and therefore will can not be burned to provide power in the engine. If 3% of every gallon has no energy, you would also expect a 3% drop in miles per gallon.
Forget Oct-Nov, that's year round for oxygenates, but different blends of it at different times.

Winter fuels have a different RVP for easier evaporation in the cold for easier starting. Different component blends and different prices.
http://www.consumerenergyreport.com/...nter-gasoline/
http://auto.howstuffworks.com/fuel-e...mmer-fuel1.htm
http://ask.cars.com/2009/02/whats-th...y-cars-pe.html


http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=633178
Living in Northern NJ we are "forced" to use oxygenated gas. Our's has MTBE as the oxygenator. Previously it was only used in the winter but a number of years ago it became a year round curse. I knew you lost some mpg with oxygenated gas, but I never realized how badly until yesterday. I had to go to Lancaster PA with my 2002 V-8 p/u truck. I filled before I left and reset the trip odo. I refilled the truck in PA and calculated my mpg, 15.03 mpg . Especially considering it was 1/2 highway at 65mph and secondary roads with very little stopping. The refill was 12 gallon of NON oxygenated gas added to the remaining 18 gallons of NJ oxygenated gas still in the tank. Got home and filled again. Calculated the mpg again and it was 21.02 mpg ! And coming home I went 75 mph on the highway instead of 65! Plus the trip home was more uphill over all. 6 mpg more represents a 40% improvement! I knew there was a difference but I didn't realize it was so great . Incidentally the wife has an Explorer and travels to see family in VA, where they have NON oxygenated gas also. she has found just about the same spread in mpg using NJ oxygenated gas vs. the VA non oxygenated gas. And I told her she was crazy, oh well .

 
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Oh it's very possible...

Here is my commute to school. Normal highway on the 57N. Not down slope.

 
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Just an update on my situation: after about 4000 miles of driving on the swapped engine, the mileage improved; it was back up to around 40 again. Unfortunately, about 3 weeks ago, I was taking the ramp from the 57S to the 91W, and apparently 80mph was too fast for the corner, a huge lapse in judgement on my part. My car began to slide and from there, there's about a half hour I don't remember. I took out a light pole, which hit right behind the driver's side door, and honestly I was lucky to have walked away with nothing but a couple scratches and a headache; I could have died. Much of the car is still in good shape; it still runs like a top, but the frame's messed up. That car was my baby, I paid cash from my own pocket at 16 and took better care of that thing than most people do their BMWs. The worst part? We had talked about getting full coverage since I moved from a rural area to the OC, but it never ended up happening; I only had liability. I'll probably never stop beating myself up over what happened. I have a friend trying to get me as much money as possible for what's left of the car; he next car will likely be a CD5/CD7 Accord. The whole situation definitely puts a bit of a damper on my freshman year of college though.

Here's the car before the accident:



And a few after:









Even after the accident, she's still clean as hell inside. Minus all the junk on the seat from the glove box, that's how clean I kept it on the daily.




Anyone know someone looking to buy something like this? It's currently located in Orange, CA :P

 
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ouch!

 
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That'll buff out......

 
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Haha right, but that still leaves the floor behind the driver's seat that feels like multiple overturned tacos.

 
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But for real, anyone have suggestions on how I could get more than $1400 out of it? Cause that's what the bid's at right now. The engine ran beautifully (only has ~50k mi) and transmission shifted as smooth as silk. I changed the tranny fluid at least 3 times in 35000 miles, oil changes every 3k-3500 miles, new ceramic brake pads a few weeks before the accident. Hell, I'm sure the wax coat is in amazing shape to this day!