Hi all
I took a 180 mi trip today on my 87 300d turbo, when I left, the gauge was at exactly half way between the 1/2 and 3/4 , when I was done the gauge was at exactly half way between the 1/4 and 1/2 mark which is 1/4 tank. Now the tank on my 300 d holds 18.5 galllons so that works out to 4.5 gal for the whole trip, thats 40mpg, can that be right? . I know my gauge is accurate. The only thing I did was cleaning out the switchover valve which was clogged with soot robbing my alda boost signal ( it looked clear on the outside but checked it anyway ) . After that the car ran unbeliveable. Has anyboby gotten this kind of mileage?

PS. The a/c was on for about 2/3 of the whole trip

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

Just because the needle moved that distance doesn't mean it only used 4.5 gallons....once it is on "R" there is around 3-4 gallons still in there, so it likely used more like 6-7 gallons in that "1/4" tank movement...which comes out to around 27-30mpg, which is more like it.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I don't think that's possible. Unless you were in extremely favorable conditions. I don't care how accurate you think your gauge is, the true test is at the pump.

I think the best my brother in law has gotten is 35 - 36 mpg in his 300D. That's without the AC, and flat 50 mile highway stretches to work and back.

I got 31 mpg in my 300SDL last tank. Best ever was 32. So I would assume, given the weight difference, the best a 300D could yield is 36(normal driving).

No matter what you read from wherever you read it. A 3.0 liter diesel cannot deliver 40 mpg unless it was driven at speeds where drag and engine speed are not factors(like the new CDI's that were tested recently).

Fill it up....Maybe I'm wrong. But I'd be right in saying, you'll never get a tank like that again.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

the only way to accurately measure mileage is to fill it drive it and fill it again. divide the miles by the gallons and you will get mpg. then do it twice more using the same pump and take an average. THEN you will have a reliable indicator.

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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.

Down hill with the engine off maybe.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Dont they also count the reserve in the total 18.5 gals? I would guess they do

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

I also forgot to mention that I was carrying 4 adults 2 of them at least 250lbs

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

has anyone heard of an inline meter that can be installed right before the secondary filter? I could swear I've seen them somewhere, That'll be really cool

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

FlowScan makes fuel consumption meters for the marine industry...probably not too cheap either.

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Never a dull moment at Berry Hill Farm.

Flowscans are great but they probably won't measure a flow as low as our cars burn. Maybe if you called them they might have a very small unit. I can't imagin that our cars burn more then a couple gph at wot.

btw Boating mag just tested a bunch of these meters this month and found them to be somewhat accurite. Flowscan read 1 gph high I think.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

If they count the reserve in the total then it would mean from the full mark to the R mark there'd be about 14-15 gallons to be used, putting approx 7 gallons between full and half, and another 7 between half and Reserve. so if it moved from halfway between full and half, to halfway between half and reserve, then it'd have likely used about 6-7 gallons........

There's a chance you may have gotten in the 30-35mpg range, but with weight/a/c on its not very likely. Best I have gotten was around 28.5 with my 617 with the car pretty light on the freeway @75mph. I'd guess a 603 would only be able to do maybe a few mpg's better.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I'll do a search to find out where we can get an accurate flow meter that can be used in our cars since thats probably the best way to measure fuel economy: X number of gallons go in, X number of miles traveled. It'll be real nice to get one with a display that can be mounted in the dash, we'll probably look at it more than the speedometer

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

The only problem with that is it's not a closed center system. It uses a restriction in the outlet of the IP to make internal feed pressure. In other words, x goes in, x - injected fuel comes out. Don't forget leakoff from the injectors. (Are you confused yet? ) You would need a flow meter in both the feed and return lines.

Filling your tank to capacity and checking how many miles traveled/gallons needed to refill to the same point is the best (and free$) way to check MPG.

(If your odometer is broken, guess. I'm guessing 21-24mpg with my leadfoot. )

LOL , forgot all about the return line, but I would assume that the manufacturer would consider this and measure both the supply and return lines and show the difference as the actual spent fuel.

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

Yes, they will sell you 2 flow meters!

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.