Cool & Happy!

[Richard Wooldridge]

Portland, OR had a 105 degree day today, and I drove my '82 380SL with 560 engine to work today- I first went into Portland, then down 50 miles or so to Salem, then back to Portland, then returned home in the hottest part of the day through afternoon rush hour traffic. I'm happy to report that the AC kept the interior of the car nice and comfy, cool even when moving faster than 20 mph even with outside temps of 105. The car's temperature gauge hovered around 100 most of the time except on the freeway, where it went down to 90 or so, and in stop and go traffic at 105 degrees it went up about halfway between 100 and the red line.
After all the negatives I'd heard regarding the climate control system, I've been worried that the AC might not be robust enough to satisfy me, but it performed heroically. It has R12, of course...

[Dee8go]

How long have you had it, Richard? I'm guessing this is the first summer from your comments.

I would have thought Oregon would not get so hot. Just a guess, though. I've never been there, unfortunately. It's hot as hell down here in VA.

[Richard Wooldridge]

I purchased the car from a forum member in March of this year, so this is the first summer with it. It had a lot of small problems that needed attention, and one major problem, the front subframe tabs that hold the lower control arm on on the left side were cracked and broke while driving my granddaughter to school... had to replace the subframe. The 380SL is a real joy to drive with the 560 engine, not many cars on the road can touch it for performance these days. It also gets good mileage, 19.8 on the freeway- better than my '79 450SL, which only gets around 17.5 on the freeway. I guess I should install a later differential in the '79 to boost the mileage a bit.
The AC works great in both cars, and they both still have R12 in them, and will stay that way. I managed to purchase 45 lbs of R12 on Ebay at a good price, so have a reserve if needed. Between my brother and I we have over 30 cars, and most of them use R12...

[rwolak]

how did you get your 450 to get such good hiway mpg? i have a '78 that only gets around 12-13 hiway and near 10 around town. the car is completely stock and has a new tuneup.

any help will be greatly appreciated.

tia

[Dee8go]

It doesn't seem logical that a 560 would get better mileage than a 450. Is the gearing the determining factor? I suppose weight would also have an effect, but surely not that much?

[Walrus]

Originally Posted by Dee8go

It doesn't seem logical that a 560 would get better mileage than a 450. Is the gearing the determining factor? I suppose weight would also have an effect, but surely not that much?

It may not seem logical, but is often the fact. The gearing on the 560 is rather stretched, at 2.47:1, and I believe the fuel management to be much better, especially when compared to the earlier d-jet 450's. I routinely get better than 18 in mixed driving on my 560. Granted I do not drive it in town (read stop and go) much, nor do I have to use the a/c much at all. Not because it aint hot in Alabama, but I do not use the car for anything other than pleasure...

[Richard Wooldridge]

Hi there,
My '79 used to get poor (er) mileage, until I fixed it... The warmup regulator was out of adjustment. There is a spring inside the warmup regulator that loses it's tension over the years and causes the pressure to the fuel distributor piston to lower, making the mixture too rich, both at idle and at speed. The best way to fix the problem is to replace the warmup regulator with a new one, but I was able to take the regulator apart and adjust the setscrew inside to get the proper control line pressure. I've driven both cars from Portland to Seattle within the last few months, and checked the mileage on each... the 560 gets better mileage, hands down. That 2.47 rear end is responsible, I think. Of course, I had the top off the '79 when I drove it, so it might do a little better with the top on, but not much, as the engine is spinning almost 1,000 rpm faster at freeway speeds.

[London380sl]

Originally Posted by rwolak

how did you get your 450 to get such good hiway mpg? i have a '78 that only gets around 12-13 hiway and near 10 around town. the car is completely stock and has a new tuneup.

any help will be greatly appreciated.

tia

How old is your o2 sensor? I've read more than a few threads that had the same mileage as you are getting. They changed their o2 sensor and the mileage jumped up.

[Richard Wooldridge]

Hi London380SL,
The 450SL didn't have an O2 sensor, they didn't start installing them until 1981, when they added the lambda control unit. The 1978 has a straight mechanical CIS system, no feedback, no control unit. I just checked the factory manual to be sure... change was in Sept. 1981...