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#31
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I log every tank. My tank was about 2/3 full when I parked it seven years ago. I got 511 miles on 16.7 gallons, which is 30.6mpg on stale fuel. It ran very well, I’m surprised. I ran 195/70r-14 tires for 383 miles and 195/65-15 tires for the last 128. Most of this driving has been 35-55 mph.
I have to look back, but my 240d doesn’t do that well because it screams on the highway. I routinely got 28-32 mpg in my 83 300D, with it more like 28-30 when driving interstate at 65+. Resistance increases cubically with speed. So it’s quite possible that you burn a decent amount more fuel to do 70 vs 65, and a LOT more than 60 or 55.
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Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#32
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One day I will find a w123 that gets 30mpg at 75mph highway driving.
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-Typos courtesy of my mobile phone. |
#33
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Even a modern streamlined car will lose MPGs much above 55. My Honda Accord Hybrid has an interesting operational zone where it’s more efficient running at 70-80 MPG than at 55 in continuous highway driving. It’s much more streamlined, and once you can’t be on the battery, I guess the engine is optimized for better SFC at higher load.
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Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#34
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Misconception on my part. I thought you were inferring the ULSD of today has no effect on the pumps used on the OM617.
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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.” ― Brian P. Cleary, You Oughta Know By Now |
#35
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And there’s tons of additives that add lubricity, perhaps the cheapest being good old TCW-3 2-cycle oil.
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Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#36
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Thank you.
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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. |
#37
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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. |
#38
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Your Honda is geared in such a way that it is more in its torque band at 70/80 compared to 55. Despite the higher engine RPM, the engine uses less fuel to make more power since it doesn't have to lug as hard. My '05 civic was an extreme example of this, it got better economy the faster you went. I routinely did 80 when the speed limit was still 70 and routinely returned 42-43mpg highway (sticker was 38). I got caught in a fast-moving bunch of traffic on I-35 (there's a concept hard to comprehend!) going to Dallas one time where the average speed was 90 (I was even being passed by the Hi-Po). Car did 52mpg on that run. |
#39
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There is something common but not totally identified. That does seem to change the acquired fuel millage from car to car. The drivers have an influence of course. Yet on highway driving at about claimed speeds. The millage reported varies too much in my opinion. It is years now and I still do not have a clue of what it is with the 240ds. One thing that did cross my mind though. If the viscosity of synthetic oil is still much less at operational temperatures. It could be a factor. I do not want an oil thread. Yet I always puzzled over the gentleman who could never get more than 25 miles per gallon on his 240d from new. When his car was new they used straight 40 weight I believe.. The 616 exibits a high power loss from the viscosity of the oil. It has no power basically after a cold start on a winters day until the oil warms up a little. I know it is a low power engine overall. Yet it is one of the few cars that have this issue as bad as it is. Taking two samples of oil. Say a conventional oil and a synthetic oil. Heat them both to say three hundred degrees and measure the viscosity present. Just might indicate that the synthetic oil increases milage per gallon. On these particular engines. As it has far less actual viscosity. A 240d with dino oil when it is cold has virtually no acceleration potential. It may pay off fuel wise to change to synthetic. At least enough to more than justify the additional cost. Now that synthetics can be purchased at deal prices from time to time. Although I do not think extended change periods should apply to these engines if you use synthetic. Without oil testing. I am also using the claims of synthetic makers. Protects like an oil of heavier viscosity. Not that it actually has it. I know from observation that a 15-40 conventional oil does not have the viscosity of a straight 40 weight when heated to operational temperatures. That is why in my opinion if you are burning oil with a 15-40 grade.. Running straight 40 weight will signifigantly decrease oil consumption in most cases. Very useful in those climates where the temperatures do not fall that low. Or late spring summer and early fall here. Providing the reason for the oil consumption is it getting past the rings. Could the viscosity of the oil at operational temperatures account for the difference? Or part of it? I just do not know. It would have some effect as that was originally the primary claim of synthetics when they hit the market. That being they increased fuel milage. The only way that was possible was less viscosity or oil drag. The molecules are perhaps larger with synthetic oil this replacing viscosity or the barrier effect to some extent. My early Mercedes gas engines I used to work on. I believe many exceeded the milage lifespan our diesel engines do in many cases. Back then they were on a diet of straight 40 weight or even 50 weight by some owners. Fuel milage was not that good though on them. Today I have to wonder if those same engines would have done better on synthetic oils. Again I do not want an oil thread other than remarks about the above. I really back no oil type or brand. Except for my beater Jetta that will eat the cam faster if you do not use specific oil. Using specific oil is both a pain but the cam lasts longer. They all still fail on that years diesel. Last edited by barry12345; 07-13-2019 at 11:03 AM. |
#40
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I do not know if diesel fuel on average ever really goes stale. In my experience old diesel fuel seemed to be okay. The risk is more water from condensation collecting in it with time sitting. Then you get growth or issues with it. These older design of engines and perhaps newer designs may also lose milage at increased RPMs. Partially because of the RPM range of operation. Good diesels vehicles try to keep the RPM down as the efficiency of the combustion process is probably better. As a crude explanation .The spread of the fuel burn front sees a piston moving away from it faster to some extent. Reducing available effort or power of the burn.Or wasteful in effect. In theory if you increased revolutions beyond a certain point the engine would not even run if the pistons velocity exceeded the speed of the burn front. You do not want to lug a diesel down too much as the thrust loadings get very high. In that condition though the fuel burn is capable of producing the maximum actual work. Or efficiency of burn. Last edited by barry12345; 07-13-2019 at 10:57 AM. |
#41
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The concept that the viscosity of a synthetic oil is less than that of a conventional oil at operating temperatures is false. A 40wt synthetic or conventional fall around ca. 14-15cSt at 100C if they are rated as 40wt oils. Doesn’t matter if it’s syn or not. It’s a classification for viscosity. Synthetics will pump better at low temperatures, especially shear-stable 5w-40 oils that offer the same protection and viscosity at operating temperature (~100C). Don’t want an oil thread either but just need to be clear on that. Syn oils may exhibit higher film strength for a given viscosity at high temperature/high shear and thus allow a marginally lower viscosity. I will say that the few 240D caramel ive driven, mine is the most willing and responsive. An AT wouldn’t have been my first choice but the car just runs. It’s not geared to be pleasant above about 55mph on the highway, but it will run to 75+ with no issues very willingly. But it’s also a 27 mpg car on highway runs because it screams at speed. I have run 5w-40 syn since almost the very beginning of ownership of that car... it is a low power car, not fast, but starts and runs well and is willing even in the cold. I can certainly see though how the loss of a little bit of power on that engine can make a huge difference, and once things get slightly off (timing, injection position, other loads), that plus some other losses can really add up and result in 10%+ loss easy.
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Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#42
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This doesn't make sense. The tank is 20 gallons or so and u ran 400 miles. So assuming you ran your tank completely dry which I doubt you did, at best you are at 20 MPG
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#43
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Noticed even on the 300sd a noticeable performance increase 10/40 vs 20/50.
Mileage increase not more than 1-2 m.p.g. My 240d averaged 33m.p.g. mixed driving,4 kids,2 adults,luggage.Some in town,Mts. freeway for 1hr 30min. 80-85 m.p.h. No gear change,stock tires except wider Not a stock 240d ,number of mods. AS knowledge has increased over the yrs. very sure could squeeze out a few more. Willing to share how if others want to know. |
#44
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__________________
Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#45
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Simple concept. If hot viscosity is the same with synthetic and dino oil. How could manufacturers of synthetic claim superior fuel millage? I think the only way to be certain is to heat two samples of oil. And time them both through something like a new paint filter each.
I would also like to see how a straight 40 oil does during the same test. It has to hold more viscosity hot than 15-40 can achieve. Again all too often I have seen quotes. Protects like a 40 weight. Running straight 30 in a car that burns oil. Can reduce the oil burning at times by fifty percent. In comparison to using 10-30. My father clued me into this a long time ago. It seemed to work well the few times I tried it. I did not check for any change in fuel millage when I did this. I am not trying to be argumentative. As far as I am aware nobody has done the simple test. The wives car specifies 0-20 synthetic of course. I have wondered if this is to push the fuel millage to the maximum. Will it shorten the lifespan of the engine is just not really known. Over running a 5-30 oil. |
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