with my truck with a 6.5L Diesel it is 65mph at 1995 RPM, My 300D seems to slurp a little more than it should. I drive a little hard and the A/C is cranked.

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1993 MB 300D 245K died.

What are you asking?

What is your MPG currently?

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

I never got over 28 mpg on my '93.

I drove it about 75 mph with the A/C on.

I got the same mpg in winter but that was with winter fuel and obviously no A/C on.

I tried everything but never got better than that.

I don't know that I've ever seen a BSFC map for your car, but this chart for a 126 should put you in the ballpark.




Here's a good discussion for understanding how to read the charts - Engine & fuel engineering - Understanding BSFC maps

The two major components are at higher speeds rolling friction and drag due to air will increase fuel consumption while at engine speeds above and below max efficiency fuel consumption will increase. The balance point will be the speed where the hp required intersects the lowest specific fuel consumption.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

I'm good then. I drive the same and get 24 MPG. I got a 10% loss in MPG to start with because I'm using 100% BioD

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1993 MB 300D 245K died.

Best I've ever seen on either of mine is about 32 mpg.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

My 91 300D gets 30-35 MPG doing 70-75 MPH with A/C on... My last 3 day run was 33 MPG, mostly at 70MPH

Cruise control is a big help too. I've been doing 75-80 on a few of the more recent fill ups... I tend to get distracted and leave late for work.




EDIT UPDATED.

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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

Mach4-Is that map for the 617 or the 603?

To the OP: Without getting really technical, top fuel economy in most cars usually happens at the lowest speed in top gear that you can run without lugging the engine. If you have a lockup torque convertor, you want to be going fast enough to keep it locked.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

617

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

I'm getting a good 34 if only highway at 70 no air con I only wished it would get that warm. 602

You'll do better running 50 to 55 mph...if you can stand it. I had a 91 300d and could get over 30 mpg running 75 or 80 only after the rear muffler wore out and I replaced it with straight pipe.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Was it noisy without the rear muffler? Was performance up noticeably?

A little growl. I liked it. No noticeable gain in performance but the fuel economy seemed to jump 2 or 3 (which seems unlikely but it is what I remember happening.)

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

If anyone cares, those "contour lines" on the graph showing g/kWh stand for grams per kWh. 1 gram of a benchmark (reference) diesel fuel has about 18362 BTU/lb or 42.7 MJ/kg, if anyone cares. 1 kW is equivalent to 1.34 HP. In the large engine biz we used to use g/kWh all the time, but in the US we usually use BTU/kWh.

This is undoubtedly a mechanical fuel consumption based on shaft output at the engine. If you hooked your diesel to a generator you could theoretically figure out how much fuel it would burn, if you ran it at (for example) 1800 RPM and knew the generator efficiency (probably 92--93% for a small one) at the output you were pulling from the generator. Just as a reference, the best large slow speed, 2 stroke diesel engines will do ~165 g/kWh.

Rgds,
Chris W.
'95 E300D, 422K

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Objects in closer are mirror than they appear.

If i drive 70 to 75 mph i never get anythning better than 32 mpg. Last time i tested it doing 65 mph with the AC on and i ended up with 35 mpg.