So a Diesel mechanic tells me.... - PeachParts Mercedes-Benz Forum

Drago · #1 07-20-2015, 08:04 PM

while having my tires rotated and balanced I had the young mechanic drain off about a quart of motor oil, I had over filled it when I changed it a few weeks ago. He said the oil was "sticky" from not driving it long enough or not warming it up long enough. I drive it to and from work which is 3.5 miles from my house and on Fridays I drive it about 70 miles round trip for daughters Violin lessons. I was told diesels are continuous duty motors suited for factories, ships, trucks and taxies. Do I need a different oil? hate the idea of wasting fuel in the driveway warming up

tyl604 · #2 07-20-2015, 08:22 PM

Look at the cans of oil. There are some oils made specifically for diesels and others made for diesel or gas. If you are concerned, use the oil made for diesels. Do not think there is much/any price difference.

dieselgirl85300D · #3 07-20-2015, 08:37 PM

on your weekly 70 mile round trip, after it warms up, floor it real good to blow out any soot. Do it a few times until you dont see any black smoke. Not warming it up good soots it up. I use rotella made for diesels. Plenty of oil debate threads.
Some will say drive it like you stole it!!! Apparently the engine likes it, now the passengers may not ...

Phil · #4 07-20-2015, 08:54 PM

Isn't sticky oil an oxymoron? Make sure you use oil designed for diesels. I have to use my car for work at the moment which mean a lot of very short trips but I make sure to change the oil at about 3000 miles.

Drago · #5 07-20-2015, 08:57 PM

been using shell rotella 15w 40 T5. Don't think Mom would appreciate me blowing the carbon out with her daughter in the car while on the way to violin practice. My daughter always rats me out.

Frank Reiner · #6 07-20-2015, 10:00 PM

Quote:

Originally Posted by Drago

while having my tires rotated and balanced I had the young mechanic drain off about a quart of motor oil, I had over filled it when I changed it a few weeks ago. He said the oil was "sticky" from not driving it long enough or not warming it up long enough. I drive it to and from work which is 3.5 miles from my house and on Fridays I drive it about 70 miles round trip for daughters Violin lessons. I was told diesels are continuous duty motors suited for factories, ships, trucks and taxies. Do I need a different oil? hate the idea of wasting fuel in the driveway warming up

These also are things that can be believed without question:

"I will always love you."

"The check is in the mail."

"Tomorrow, without fail."

mach4 · #7 07-20-2015, 10:35 PM

I'd like to see you drive your car more to ensure it gets up to operating temperature....oh, and consider getting a new mechanic, preferably one with a bit more experience.

dkr · #8 07-21-2015, 03:55 AM

x2 about the new mechanic. In general, there's no need to let the engine warm up but it's good to take it easy on the throttle until you reach operating temperature. Diesels are meant to be run under load, not idling.

Dkr.

mannys9130 · #9 07-21-2015, 04:14 AM

Diesels, especially prechamber diesels, burn most efficiently when under load. To warm up the car in the driveway is a bad idea. Start the engine, attain oil pressure, count to 5, and then drive away. I get in and turn key to glow, put on my belt, start it, open the windows and turn on the radio, and go. Drive gently (less than 2500rpm 3k at most) until the engine is at temp and the oil is hot. Those short trips are very bad as far as operating parameters are concerned. It's automotive torture. The 70 mile trips will boil out any condensed moisture though, so your OCI shouldn't suffer too badly in the long run with not much time to create acids within the oil (the additives will also deal with that).

Nobody can tell if oil is good or bad by looking at it. Not one person on this entire planet can tell if oil is bad by feeling it. It's simply impossible.

Your circumstances aren't changeable, so I say stick to your 70 mile regiment, use quality fuel and oil, and stick to a 3k mile OCI very closely. It'll be fine.

Maxbumpo · #10 07-21-2015, 07:21 AM

Manny has nailed it. If you are REALLY curious, send a sample of your oil in for analysis. Prof. Google can find many labs that analyze used engine oil, make sure the lab you select can also report the soot load percentage. Oil thickening / thinning (viscosity) and soot load are what you want to determine, wear metals are fun to know as well.

dude99 · #11 07-21-2015, 11:05 AM

Quote:

If you are REALLY curious, send a sample of your oil in for analysis.

This... If its really bothering you analysis is pretty cheap. See what it says... Anything more is just conjecture at this point. Also, I think your mechanic is full of it.....

Diesel911 · #12 07-21-2015, 11:33 AM

In theory short trips do not heat the Oil up enough to get rid of moisture and don't get hot and expaned as much and that means the do not seal as well as when hot.

On top of that the Fuel burns better when the Cylinder Head is up to operating temp.

Both will cause more contamination then if the Engine was warmed up.

If you look at some old Auto Repair Books it will say that short trip stop and go driving and frequent long full load runs are conswidered severe useage and it will say to change the Oil at a shorter interval.

In my case My Wife drives the Mercedes about 2 miles to work. In the Moning she gives it about a one minute warm up and then takes off. Not sure what she does on the trip back.

I try to get the Mercedes on the Freeway on the weekends if I have someplace I need to go.

If you decided to add on a Bypass Oil Filter in theory that takes care of any Soot Particles in the 0.5-2 micron range. Won't help with any moisture build up issues.

http://www.peachparts.com/shopforum/diesel-discussion/168135-pass-oil-filter-install.html

I have had experimented and have had 3 different Bypass Oil Filters on My car. Currengly I am using a Frantz Toiilet Paper type element bypass oil filter.

Eventually I would like to have the bypass oil filters on all of my vehicles but have never taken the time to do that.

BillGrissom · #13 07-21-2015, 02:33 PM

90% of mechanics comments are towards scaring up more work, needed or not. Especially brake and transmission shops that lure you in w/ "free inspection". Most mechanics are paid mostly by the job, not a flat rate, so they have an incentive to find things.

winmutt · #14 07-21-2015, 04:28 PM

It takes ~20min to burn off water in eng/trans/diff oil. Since Fridays you get a good distance in, I wouldn't worry too much. Short trips are generally not engine friendly.

Charlie Foxtrot · #15 07-21-2015, 06:48 PM

Not sure what the mechanic is seeing/feeling, some oils are tacky, others are slick. Short runs are an engine killer. Diesels are designed to be run under load for best results, but if the run isn't long enough to get the engine up to temp, I'd be inclined to let it warm up. In aircraft there usually is an oil temp gauge so the pilot an keep the engine's oil in the proper temp range (a cheap aircraft engine is $15K-$20K). Ditto for expensive diesels (power stations, ships, etc). The oil needs to be hot enough to drive off the moisture otherwise acids and other nasties form. I'm curious about the Franz oil filter - why did you think it was needed? I used to install those in the 60's & 70's in taxis and delivery vans. Kept the oil looking clean. The fleet owners used oil analysis to dictate oil change intervals. Seemed to help with longevity.