I filled up the 1978 6.9 today after going through a full tank for the first time with a working odometer. It's my habit to check the MPG's after each fill up for my cars. I was pleasantly surprised to see 19 MPG, which I think is fantastic for a 37 year old, 6.9L, 2 ton, V8 sedan. My daily commute is 16 miles one way on mostly local 55 MPH highways. What do you get for fuel economy, average and all-time best?

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1987 300SDL

19 sounds good for a 6.9. I've heard 10 as a ballpark figure.

I don't have a 6.9. I've been getting 25-27 with a 300D and 45-ish with a Triumph Street Triple.

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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 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.

I have a '97 CL600 and I get 18-19 on the open road. I don't even look at what I get in city driving with the AC on. And hexaflouride, you will get a better average if you fill up, note mileage and go through 3-4 more tanks noting gallons and note the ending filled mileage.
Anziani
'97 CL600 51K

13mpg in the '74 450SLC, 15 in the 5.0 swapped '88 Supra, and about 18 in the box Vic. Speedo and odometer don't work in the E320.

Wife's 00 S430 gets 22-24 mixed driving, 27 hwy. My 94 E420 gets 20-21 mixed, 24 hwy. My 80 240D gets 27-28 mixed, 32 hwy. Don

My 94 wagon gets 33 mpg, one tank never exceeded55 mph got 36, now has 220,000 miles, speedo is accurate, my 2009 e 350 gets 25-26 at high speed 80-90 gets better mileage got 28, my f 150 gets 9-10 mpg jighest 19.1 with tail wind, usually 15-16mpg on highway

I typically get mid 20's on all of my cars. My 91 300TE wagon has been pushing 28MPG since I swapped in a 5 speed. Before the swap it was lucky to get 20 MPG

5spd manual w124 is a beautiful thing.

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CENSORED due to not family friendly words

Fuel economy is an oxymoron, particularly when applied to a 6.9. Not intending to bust any bubbles, but I suggest the testing be repeated several times - then report back. One tank does not constitute a statistically significant sampling.

Right on ejboyd5, There is no way in the world that 1 tankful is meaningful. Fill up tank, note beginning mileage, note number of gallons for 3-4 tankfuls, fill up tank, note mileage. Subtract first/last mileage and divide by number of gallons. Any other method is folly.
Anziani
'97 CL600 52K

Consistently get 35-36 mpg with my 190D 5-spd stick.

The 300CE only gets 22-24, and that drinks premium fuel.

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-Steven

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1959 190b, totalled
1968 220D, sold
1969 230/8, sold
1980 240D manual, gave away at 300k (stupid me)
1985 190D 2.2 manual, gave away to a youngster
1989 300CE, sold when I retired - major regrets

Ditto on the 300CE remark....and that's better than my 2014 ATS 2.0 T.

I recently did a highway drive to the Delaware shore from DC in my '01 E320 4-Matic wagon w/135k. Speeds ranged from 55 up to 77, AC off, averaged 45mph w/25.9mpg. No complaints from me.

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....just drive'em!
'89 300TE White w/Blue, 152K SOLD!
'93 300E Blue w/Tan, 154K SOLD!
'01 E-320 4-Matic wagon, 130K
'67 Vette Conv. White w/Blue, 217,421K

Not a 6.9 but my 300CE-24 gets 35 MPG (UK) on a long motorway run but stop/start in Paris, don't ask! About 15!!!

Oh well.

RayH

My all time best* was 62 mpg on regular. I fueled up, went to work and back, then took a pleasure ride from Carson City, NV, to Folsom, CA and fueled up again in South Lake Tahoe, CA, on the way back. This was with a 2007 Kawasaki Ninja 650. Worst was 3 mpg on JP-8 on multiple convoy missions in Iraq driving an up-armored 1990 International Paystar 5000 hauling 32 cubic meters of gravel in an end dump trailer. Unloaded, that truck got 6. Good thing I wasn't paying for the fuel.

*One time when I was a midshipman I got to ride USS Kamehameha (SSN-642) for a couple days. For a while they let me drive. Despite the boat weighing 8,000 tons and having 15,000 horsepower, I'll bet the amount of 20% enriched uranium I went through on that trip was pretty minuscule. Naval nuclear power for the win!

__________________
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 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.