I just got back from driving my 82' 4 speed 240d for a 30 mile drive at 4500' Elevation.

I had er up to 65mph at one point.. she has a sweet spot at 63mph and she just hums along.

I notice my temps don't get up very high and maybe I'll experience less economy if not dialed in. I am running about 60c on the gauge. Not sure what that is in farenheight.
Anyway.. this is a car from Vegas and now resides in Utah. What is optimum temp?

thanks guys

I would say optimum is right past the 80C mark (needle pointing straight across essentially) 80-85C is optimum.....60C is way too cool, you probably have a stuck open thermostat preventing the temp from getting to where it should be, 60C will decrease combustion efficiency and can probably increase engine wear/reduce power.....I'd look into the thermostat.

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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)

This is very likely the t-stat. Search for other postings on correct type to use, and correct replacement procedure. Gasket placement and refilling system with coolant are some of the problem areas, so be sure to read up on these.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

is probably missing. with out it the car wont heat up to proper operating temp if the ambian temp is cool and wont cool properly when it is hot out.

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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.

I agree - t-stat is probably gone.

My 240D ran at about 82C most of the time with a new t-stat. Be careful when you remove the screws that hold on the cover - they can break. Hit them with PB Blaster the day before and tap them before trying to remove.

It's not a big deal if they break - I was able to retap the hole and use a larger screw when mine broke.

Might as well drain and replace the coolant and replace the radiator hoses while you're at it - not a hard job. When you refill the radiator, park uphill if possible - it makes getting the air out a bit easier.

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer

Agree with all above. Mine stays at 82 consistently.
I did a multi flush, water pump, Tstat, hoses, belts job a couple months ago. Don't use any goop on the Tstat gasket - the PO had gobs of that crap at the Tstat gasket and the water pump gasket. The Tstat gasket is rubber and seals nicely. Make sure you put it back in the proper direction and rotation - there are posts about it. Soak your bolts, they are small and fragile. I used the same ones over on the Tstat but replaced all the bolts for the water pump - they had seen much better days

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

Thermostat has gone bad, or missing. My Daughters 240D did this. Replace the T-stat and its back up to the 80-90 range.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car