M103 Fuel Economy
 

I have had my 300E for almost 6 months now and in that time I have driven it almost 5500 miles. I have been keeping a log of all of my fuel stops and I finally got around to logging them into fuelly.com and I was surprised at the result. 24 MPG average with my best tank at 28.1... Not too shabby however I have had the 300TE for almost two months and driven it about 1100 miles and it is only getting 20 MPG. Is the manual transmission really good for an additional 4 MPG?

In a word, yes.

I wouldn't be surprised. You get both an overdrive gear and lose the non-locking torque converter.

Remove the R16/1 resistor, and performance and fuel economy, especially with a manual trans will be even better. You can shift at 2000 and keep up with traffic.

Search R16/1 if you're not familiar with that item.

If ambient temperature is less than 70F and coolant is not much more than 80C, it will run detonation free on 87 PON

If ambient and coolant temperatures are higher you can get some low rev/high load transient detonation, like on upshifts, but you can "drive around" it by increasing shift speed.

Install the OE resistor for emission testing, but if your numbers are marginal short the R16/1 connector and they will go down, but the engine is totally gutless below about 2000 revs.

Duke

My 1990 300E even when running well barely would do much over 18.5 in the city and maybe 23 highway....its just a thirsty engine with the CIS-E injection.....

consistently 24 on the highway... never have driven a full tank in the city ...but i would guess 17....

don't know how folks get more than 24 on the highway... unless you drive about a consistent 60 mph... my average is at about 78 mph

The wagon is considerably heavier too, but 20 mpg is pretty good. Is that combined city/highway driving? I recall our 300TE used to get 16 city.

CIS-E and lack of overdrive the main culprits. Still, I love the M103.

I love my CIS M104, 5-speed auto and that's capable of nearly 30 mpg on an long run of up to 100 mph. But our gallons are bigger so I shouldn't boast!

RayH

It's about 50/50 split. The manual does run about 5-600 rpm lower on I95 but I'm not sure if that is a difference in gearing or the transmission. If my wife could drive a manual I would get one for the wagon too :D

88 300E
 

My 88 300 E gets about 20 to 21 mpg every tank full I keep really good track of it its always been the same never changes no matter how I drive it or ac on or off dosen't make that big of a difference either. It is an auto trans

Personal best with a 87 300E at 220K miles was 23MPG 100% highway. It wasn't really using oil, but take into consideration when I sold it and that last # was recorded it needed the fuel distributor to be rebuilt. She wasn't 100% on her game.

I get 17 mpg mixed on my 190e m103. Just replaced the injectors and am about to replace a known bad air flow meter. I also replaced the charcoal canister and related valves which it turns out wasn't even connected. I suspect my mpg will improve.

17 / 24 mpg sounds about right from when I used to have a 300E. (way back when)

In comparison our 2005 C240 is about the same weight as my 300E was (slightly heavier). Has all wheel drive, and a 2.6 liter 168hp engine, but it does a solid 20mpg city and 24-25 highway at 75mph. Without 4matic those numbers would be about 3 higher each.

My brothers "modern 300E equivalent" 2002 E320 does about 23 city and up to 31-32 highway in the right conditions.

I agree, the M103 is still a sweet sounding engine when running properly. It just seems to be a LOT harder to keep it that way than with the other engines. :eek: