In a 24-year old car, how much is too much... - PeachParts Mercedes-Benz Forum

300DPETE · #1 10-23-2005, 08:58 PM

I did a road trip in my 1982 300-D over the weekend, and as noted in another thread, was surprised to see just how much smoother the car ran at 85-90 mph.

I drove it as fast as 95 mph, but backed off...not only because it's against the law, and didn't want to get a ticket, but also because I was thinking "this is a 24-year old car, should I be doing this...is something going to blow in the next few seconds?"

What are your thoughts? Not that I ever want to go that fast again, but what is the safe (in terms of engine life on an older car--146,000 miles) top speed to be driving in these cars?

Thanks,

Pete.

Hatterasguy · #2 10-23-2005, 09:01 PM

I depends on what kind of shape the car is in and how well you know the car. I know my SDL top to bottom and know all suspension and driveline parts are as good as new. I wouldn't think twice at setting the cruise at 115+ if it was legal.

Now the 300SD on the other hand well it is in good shape but not the best. I'll be staying within the legal limits with it.

BluEyes · #3 10-23-2005, 09:45 PM

I have done a few full load max RPM tests recenty in my '71 220D. But, it had a MB remanned engine put in sometime in the last 15 years.

I have had both my '65 Chevy Nova and '70 Cadillac up above 100mph on occasion though.

I basically agree with hatterasguy. If your car is in good shape, you keep good oil changes, etc. Then there is no reason to baby it any more than you would any other car. Just don't treat it like alot of people treat their new cars, because those guys really aren't planning on their car lasting 20+ years anyways.

#4 10-23-2005, 09:47 PM

How good is your credit score?

If the rod's are not banging, run it as hard as you like! It will be a long time before they let go! In the mean time just keep the oil changed and you will probably get tired of driving it before it signs off!~

braverichard · #5 10-24-2005, 06:13 AM

Pete,

I've often asked myself the same question. I mean, my 300SD seems to be quite solid and stable at high speeds and I don't get a feeling of fragility while driving it. Even though it is 21 years old, I feel it can run the high speeds. Its suspension components are all in great shape so I don't see any risk in setting the cruise control at 90mph for 4 hours straight. I think your car's engine can handle the high speeds, just worried about the actual body/suspension of the car, given the age and the fact that it is a W123.

andmoon · #6 10-24-2005, 10:35 AM

My 78's sweet spot starts at 110mph and ends at 113mph. Smoothest!

Schmohey · #7 10-24-2005, 12:18 PM

I took an 800 miles round trip in a day last year. Was doing 95+ on my 85 300D. That thing was smooth, but once going over 100, the car started to shake, seems as if something is loose and is banging. I slow down to 95...

1983/300CD · #8 10-24-2005, 01:01 PM

It isn't speed, but RPM's that you should be concerned with. Diesels aren't built to be high RPM engines. They can drive forever at constant RPM's as evidenced by big rigs, but F1 cars they are not.

braverichard · #9 10-24-2005, 09:09 PM

I think both are important: rpms to ensure that the engine and transmission are actually up to the task, and then vehicle speed to ensure that the chassis and body are up to that tasks. As we all know, after so many years, many suspension components get weak and fragile unless replaced.

bill murrow · #10 10-24-2005, 09:27 PM

In addition to the above I would check the flex discs and be sure the brakes are up to snuff.

Cheers,

Bill