Anybody Use Straight WT Oil - PeachParts Mercedes-Benz Forum

86-300sdl · #1 02-24-2016, 04:08 PM

Flame ready...LOL

But seriously do any of you in hot climates (I'm in the south west) use straight 30wt or 40wt.

My SDL (603) owners manual says 20-50wt. Over the last 425,000 miles I've run dino or syn & always 5-40w or 15-40 'cause I could not find diesel rated 20-50.

I don't burn any (1/2 qt) per change at 3k but the lifters will tick after longer trips across the desert and around oil change time. I have put in lucas stabilizer on occasion (summer months) and it seems to quiet things down.

I know I probably should update the lifters but I'd like to wait till I'm ready to do a valve job / gasket etc. Maybe later this summer.

Footnote: Ambient air temp is now 50*F minimum, and in a few months up to 115*F so I'm not worried about hard starts.

So with an older motor (425,000 miles & no blow by) is it ok to try a straight wt oil?

P.S. I've read many a thread. Just wanted a fresh opinion.
P.P.S. I realize a multi-grade 15-40 wt is supposed to be equivalent to a 40wt at operating temp.

Thanks again!

engatwork · #2 02-24-2016, 04:24 PM

I'd continue to run the diesel rated multiviscocity syn oil if that is what you are running. I put 30W in small lawn mower engines only. I would not worry too much about lifter noise at that mileage. Has the timing chain guides been replaced?

DieselPaul · #3 02-24-2016, 04:30 PM

I don't see how 30wt is going to run quieter than 5/40. I'd keep running synthetic 5/40.

thatguy · #4 02-24-2016, 04:38 PM

IMO straight weights are kind of yesterday's news, no reason or benefit to running them in your engine vs. a 15w40 or 5w40. I know some oils are "louder" than others, but with no ill effect on engine lift; at least that's what I've read over on bobistheoilguy.com.

I think the best thing to, short of mechanical work, is to research the "quietest" engine oil if you're bothered by the sound. Some may have more moly or such to keep things a little quieter. I know gas engine guys with noisy Japanese engines like some of the Pennzoil stuff vs. Mobil 1, simply because it quiets engines down a bit more than the latter; but neither one "protects" any better really based on used oil analyses.

Worth a shot.

mannys9130 · #5 02-24-2016, 05:37 PM

No... Straight grades have been obsolete for decades.

5W-40 diesel oil is the best. I run it year round in Tucson. My lifters used to tap and tick all the time, so I replaced them. Now they're always silent and it's wonderful. Replace yours and run the 5w-40 synthetic.

86-300sdl · #6 02-24-2016, 06:05 PM

Ok...thanks for the tips.

I'll stick with multi-grade...thanks

Thinking about trying Walmart CJ-4 super tech just cause I change oil every 3 - 5 weeks or so.

Unless.....y'all advise against it.

thatguy · #7 02-24-2016, 06:06 PM

Quote:

Originally Posted by mannys9130

No... Straight grades have been obsolete for decades.

5W-40 diesel oil is the best. I run it year round in Tucson. My lifters used to tap and tick all the time, so I replaced them. Now they're always silent and it's wonderful. Replace yours and run the 5w-40 synthetic.

I've been running Delo 5w40 syn in my OM606-powered E300 for a while and really like the UOA's it's returned. I see no downside (aside from cost, but over 5-6k that's immaterial) of running the 5w40 in my engine, it doesn't leak or burn, and when hot I have the exact same oil pressure as standard Delo 15w40, even in the desert at 120*F.

Where I really see a difference, however, is in the mountains in the winter. It REALLY turns over effortlessly when it gets around 0*F and has sat outside unplugged for a couple of days. That has to save the starter, among other things, when the temps get chilly. Good stuff.

leathermang · #8 02-24-2016, 07:07 PM

I am 67.
I AM 'yesterday's news' .
I have always changed to straight 40 wt in my cars, gas and diesel , after 100 k miles.
On gas engines I also put new oil pumps on them every 100 k miles.
When I read what small air cooled gas engine mowers are supposed to use I decided that straight 30wt was just what I wanted..( up to the higher mileage ).
I do not think oil choice should be made on ' noise' but on ability to lubricate those parts which at high miles are getting father apart... like the crank to rod bearings. etc.
I put over 300 k miles on an R4 Toyota engine and then sold the car.. it was still running three years later... I use straight 40wt Delo 400 in my Ford 5600 diesel tractor and in my 240d.
I live in a climate where I do not need to worry about cold weather excess viscosity.
If I lived in a cold weather climate AND could not use the block heater I would go to the recommended by MB specs.

Clemson88 · #9 02-24-2016, 08:18 PM

Isn't multi-viscosity oil supposed to get thicker (higher viscosity) as it warms? I wish I had a viscometer.

mannys9130 · #10 02-24-2016, 09:07 PM

No. Multiviscosity oil behaves in 2 different ways.

The first number is how it's graded when cold. The "w" denotes that it's suitable for use in winter. The second number is how the oil is graded when hot. So a 5w-40 will flow like a straight 5 grade oil when cold, but it won't get any thinner than a 40 grade does at operating temp.

Straight grades are WAY too thick when they're cold. They cause oil starvation at startup and during higher rpm than the oil pump can provide flow to protect. Multigrade oils are the best of both worlds and have been the standard for decades. They flow quickly when cold to minimize the amount of damage done at startup from oil starvation, and they behave as a single grade would when fully warmed so that the oil isn't too thin when hot (like a straight 5 grade would be).

Pressure is resistance to flow. High oil pressure isn't always a good thing. You need 10 psi per 1000rpm to be safe. Too high of an oil pressure only means less flow is occurring. Bearings need oil flow to maintain a barrier film separating the contact surfaces.

With recent understanding in lubrication design, straight grade oils have been left in the past where they belong, and thin multigrades are realized as the lubricant of choice. 0w-20 and 0w-30 are common place as well as 0w-40. The oil flows very easily when cold due to its 0w grade, but behaves like a 40 grade when hot just like a 5w-40 or a 15w-40 oil does. 0w-16 oil is set up to become the next viscosity that's adopted for OEM's to spec.

Your engine will love you as long as you don't pour in straight 30, 40, 50 grade molasses.

leathermang · #11 02-24-2016, 09:21 PM

Manny, these engines are not old VW air cooled engines where high viscosity can blow out the oil cooler....
They have pressure valves and thermostats that deal with times when the oil is ' too ' thick..

mannys9130 · #12 02-24-2016, 09:50 PM

Quote:

Originally Posted by leathermang

Manny, these engines are not old VW air cooled engines where high viscosity can blow out the oil cooler....
They have pressure valves and thermostats that deal with times when the oil is ' too ' thick..

Greg the fact that you don't see what's wrong with excessive oil pressure in relation to bearings proves that you can't speak authoritatively on the matter.

Clemson88 · #13 02-24-2016, 09:59 PM

Quote:

Originally Posted by mannys9130

No. Multiviscosity oil behaves in 2 different ways.

The first number is how it's graded when cold. The "w" denotes that it's suitable for use in winter. The second number is how the oil is graded when hot. So a 5w-40 will flow like a straight 5 grade oil when cold, but it won't get any thinner than a 40 grade does at operating temp.

Straight grades are WAY too thick when they're cold. They cause oil starvation at startup and during higher rpm than the oil pump can provide flow to protect. Multigrade oils are the best of both worlds and have been the standard for decades. They flow quickly when cold to minimize the amount of damage done at startup from oil starvation, and they behave as a single grade would when fully warmed so that the oil isn't too thin when hot (like a straight 5 grade would be).

Pressure is resistance to flow. High oil pressure isn't always a good thing. You need 10 psi per 1000rpm to be safe. Too high of an oil pressure only means less flow is occurring. Bearings need oil flow to maintain a barrier film separating the contact surfaces.

With recent understanding in lubrication design, straight grade oils have been left in the past where they belong, and thin multigrades are realized as the lubricant of choice. 0w-20 and 0w-30 are common place as well as 0w-40. The oil flows very easily when cold due to its 0w grade, but behaves like a 40 grade when hot just like a 5w-40 or a 15w-40 oil does. 0w-16 oil is set up to become the next viscosity that's adopted for OEM's to spec.

Your engine will love you as long as you don't pour in straight 30, 40, 50 grade molasses.

Do you have a viscometer?

mannys9130 · #14 02-24-2016, 10:14 PM

Quote:

Originally Posted by Clemson88

Do you have a viscometer?

Nope, don't need one.

These links will show you exactly what you'd find if you owned one.

This is a series covering several different topics. Hold onto your hat, you're in for quite a large amount of oil knowledge.
Motor Oil 101 - Bob is the Oil Guy - Bob is the Oil Guy

Putting the Simple Back into Viscosity - Bob is the Oil Guy - Bob is the Oil Guy

Once you're in the know, things become very clear.

leathermang · #15 02-24-2016, 11:16 PM

Quote:

Originally Posted by mannys9130

Greg the fact that you don't see what's wrong with excessive oil pressure in relation to bearings proves that you can't speak authoritatively on the matter.

Ever looked at a blowup ( no pun intended ) of the 617 lubrication system ?
It is called a relief valve and it is before any bearings....
On page 18.8-005/1 f2 the numbers on the line drawing describe (1) as '' Oil pump with integrated pressure relief valve ''

However , IF you want the FSM to say what I have said.... then look carefully on 01.8-030/1 f2 in the 617.95 FSM
or 00.4-110/1 in the 615,616, 617 na FSM

It shows for constant ambient temperatures over 32 degrees F that three oil viscosity ratings are listed.... up to 86 degrees F.
those are ****Straight 30 wt ***, 20w-50 , 20w- 40
Note (1) states that at over 86 degrees F that *** straight 40 wt *** may be used. The stars were added by me in case your bias might cause you to misread the list.
So above 32 degrees F straight 30 wt and straight 40 wt are listed as acceptable oils for our engines.

I go heavier once an engine becomes ' high mileage ' , which I define as 100k miles and above, because as engines wear the clearance in the bearings becomes more and the thicker oil protects against metal to metal conditions better than thinner oils.