Best choice for a 6.2 GM diesel

[The_Eric]

I was wondering why GM recommended straight 30w for normal operation of that engine. It's in a 1986 Suburban. The chart on the visor of the Suburban shows it (30w) alongside 15w-40 down till about 30* F and has "Recommended" in the little arrow illustration. What was their rationale??? Since the 15w-40 is also listed in the high range of the chart, and down lower, would it be better just to run that???

Thanks for all your input!

 

[c502cid]

I've had a couple of these motors over the years and I ran them on anything I had around. My experience is that 6.2's don't really care what you put in 'em. Fresh oil turns coal black in about 15 minutes of running it though!

 

[Texan4Life]

I would run a HDEO xxW-40 of your favorite brand.

 

[sparkplug]

Can't go wrong with Rotella.

 

[ZZman]

I agree the Shell Rotella T6 5w-40 would work great for your climate.

 

[Zaedock]

I used Delo 15W40 and SAE30 in my '83 6.2L. It worked great and the truck was finally retired at 485K miles due to other issues and not the engine.

 

[wwillson]

We had several of these engines for farm use that racked up around a million miles altogether. We always used John Deere 15w-40 in the spring/summer/fall, but for the winter you'll want 5w-40 if it sits outside. Your starter will last MUCH longer with thinner oil in the winter.

Wayne

 

[addyguy]

For the summer, ANY 15W-40 you can get for a good price will work well.

For the winter, you might want to consider a 5W-40 or even 0W-40 synthetic.

 

[Jim Allen]

I divide things up a little more than the previous posters. In a cooler climate, or with light work, a 10W30 HDEO. For an engine in good shape, it offers plenty of protection, marginally better fueI economy and good cold starts. In a warmer climate, or with a lot of continuous hard work resulting in high oil temps, such as towing, a 15W40. Or a tired engine. The harder-to-find missing links between those choices would be a 5W40 HDEO or the new Rotella T-5 10W40, or even the new T-5 10W30 semi-syn.

I had a 6.2L in a Blazer for many years in Colorado and during the winter or on cold mornings, the heavy oil was a serious liability to cold starts if the truck wasn't plugged in. As the previous poster said, they are not all that particular about oil, except (IMO) when it comes to cold starts. MIne needed to spin over well to start well and the heavy oils tended to make that problematic... especially if I was in an inconvenient location (oh, like being camped at the top of a 11,000 foot pass one frigid morning).

Mine had an oil temp gauge and, because of the factory engine oil cooler, I found that the oil usually ran pretty cool, even in hot weather. My criteria for viscosity choice is oil temp, which is related to ambient temp and workload. The oil in mine almost never reached 212F (the viscosity rating point for motor oil). In hot weather (100+F), the normal high oil temp was around 205-210. In the 80s and 90s ambient, a few scratches below 200F Consistent oil temps over 212 would be the indicator that a thicker grade was in order due to the thinning process from heat. Occasional spikes over 212 are no worry, unless they get wildly over and stay there for a long periods. I didn't tow with it, but I four-wheeled a lot in Utah and even on 100+degree days rockcrawling at 1 mph, the oil seldom got overly hot. Transmission... that was another matter!

 

[JHZR2]

I might imagine that back then, before the more shear-stable VIIs that were around, 15w-40s in a relatively small sump (compared to HD trucks), perhaps there were viscosity retention and shearing issues... Just like why 10w-40 oils of the same vintage got a bad name.

These days, Id run 15w-40 and not think twice. I'd also consider 5w-40 and perhaps even 10w-30 HDEOS too.

 

[The_Eric]

Originally Posted By: wwillson
We had several of these engines for farm use that racked up around a million miles altogether. We always used John Deere 15w-40 in the spring/summer/fall, but for the winter you'll want 5w-40 if it sits outside. Your starter will last MUCH longer with thinner oil in the winter.

Wayne

When I bought the truck, the starter was toast from the last owner trying to start it in the winter with low batteries and without plugging it in. Therefore I got another right off the bat (the other was lifetime warranted). The new one was a gear reduction unit and it has a much better go of things when it gets chilly. Speaking of that, I always plug it in when the temp drops and it spins over like a top and starts easily with 2-3 complete cycles of the glow plugs.

Originally Posted By: JHZR2
I might imagine that back then, before the more shear-stable VIIs that were around, 15w-40s in a relatively small sump (compared to HD trucks), perhaps there were viscosity retention and shearing issues... Just like why 10w-40 oils of the same vintage got a bad name.

These days, Id run 15w-40 and not think twice. I'd also consider 5w-40 and perhaps even 10w-30 HDEOS too.


I was wondering about that but since I don't know much about the history of oils, I wasn't sure.

I did notice that it was slightly more rattly (if that's possible) at cold start up with the 15w-40 than with the 30w.... Nothing to be concerned about right? It carries about 20lbs hot at idle and 40-45lbs running down the road.

 

[Fordiesel69]

If you ditch the GM side post batteries and install 2 true 750CCA or better batteries, and then add a push button for the glowplugs, starting will be much more enjoyable. 15W-40 will even work well in the winter. No need for the thinner stuff as this stuff did not exist back in the day for this engine. They still lived long lives.

Take a newer CAT or Navistar engine with HEUI injection system and thin oil is a must for any kind of cold atart performance.

 

[bullwinkle]

Originally Posted By: c502cid
I've had a couple of these motors over the years and I ran them on anything I had around. My experience is that 6.2's don't really care what you put in 'em. Fresh oil turns coal black in about 15 minutes of running it though!
Interesting-I've had 2 6.2s and they both are/were much better about turning the oil black than the new Dodge or the Mercedes-wonder how your injector nozzles/spray pattern is doing? Also running straight 30 Delo 400 in my '93, year-round, doesn't seem to slow crank speed too much until it gets below 0* F.

 

[The_Eric]

Originally Posted By: Fordiesel69
If you ditch the GM side post batteries and install 2 true 750CCA or better batteries, and then add a push button for the glowplugs, starting will be much more enjoyable. 15W-40 will even work well in the winter. No need for the thinner stuff as this stuff did not exist back in the day for this engine. They still lived long lives.

Take a newer CAT or Navistar engine with HEUI injection system and thin oil is a must for any kind of cold atart performance.


Yup, that's the first thing I did when I got the truck. Once I got it home, I beefed up the cables with 1 or 1/0 gauge welding cable and solder on ends.

What does the push button do that the key doesn't?

 

[Jim Allen]

Originally Posted By: Fordiesel69
If you ditch the GM side post batteries and install 2 true 750CCA or better batteries, and then add a push button for the glowplugs, starting will be much more enjoyable. 15W-40 will even work well in the winter. No need for the thinner stuff as this stuff did not exist back in the day for this engine. They still lived long lives.

Take a newer CAT or Navistar engine with HEUI injection system and thin oil is a must for any kind of cold atart performance.


Some incorrect info above in red. I still have some of the manuals for my '83 6.2L. I'm looking at the factory manual now. The oil viscosity chart shows SAE 30 from 32F to 100+ and the bar says "PREFERRED". The 15W40 bar goes from 0F to 100+ and the 10W30 runs from below -20 to 60F. More modern oil formulations would leave a bit more flexibility in choices, IMO, both for the thick and thin. Back in '83, the 10W30 and 10W40 oils were less shear stable than they are now., for example, so newer charts show the 10W30 going into higher temperature ranges... at least as far as the single grade 30 did in my example. Also, the 15W40s have better cold weather performance too.

The tip about the batteries is a good, and one that I did too. The glow plug tip is good too, EXCEPT, you can't do that with the factory glow plugs. They will fry and possibly drop their tips if you exceed about 10 seconds of glow time. Ask me how I know? To do this, you need HD glow plugs. The ones I found that won't fry no matter what come from Kennedy Diesel, but there are some Delco replacement numbers that are good too. I just don't recall what they are.

I guess how an engine cranks over in cold weather is pretty subjective. I had so many starting problems with my 6.2L, many of them related to cranking over in the winter in remote locales. I started with stronger batteries and 00 gauge battery cables. A new starter came along too (several in fact). It got a pump and injector replacement along the way, a compression test, a manual override button on the glow circuit and Super HD glow plugs and finally 10W30 oil. The oil is what finally got it 100% reliable on those zero or below zero days when I couldn't plug in.

Conversely, my 6.9L '86 Ford diesel (which I still have) could always start unassisted on below zero days, even with 15W40 (though I often use 10W30 in it as well these days). I have a Ford diesel tractor that I use for plowing and snow removal in the winter and shortly after getting it, I found it would not spin over to start reliably below about 15F with 15W40, even after a new battery and 00 cables, until I switched it over to 10W30.

 

[Jim Allen]

Originally Posted By: The_Eric


What does the push button do that the key doesn't?


The factory controller doesn't cycle quite long enough. IIRC, they are 5-6 second glow times, which is about all the factory "fast glow" glow plugs can take reliably. On a cold day, the engine might like 10-12 seconds (that was my engine, I suppose there are variables that could make it go higher or lower). The problem is that 10 seconds or more on the factory glow plugs (or the aftermarket direct replacements) is problematic. I found them frying anywhere close to 10 seconds. Sometimes, they blister and swell, making them a bugger to get out and sometimes they drop a tip into the engine. The Kenendy plugs had a narrow tip and I once hooked one up to a fully charged Optima battery and let it glow until the battery was nearly dead. No fry! The next best plug I tested lasted 30 seconds or so. That was late '90s, so things may have changed today, but if you get on the 6.2-6.5 Diesel Page, you can find out what's the best currently.

 

[bullwinkle]

If you change them to the 60G glow plugs then they can take anything (but you'll need a switch or controller mod to make them stay on long enough)-the stock 9G ones were the troublesome ones, that's why I mentioned the condition of the injector nozzles (high mileage?)-if they drip/leak fuel they can cause hard starting and possible fuel dilution/black engine oil, and the 28MT gear reduction starter used on the later 6.2 & the 6.5, along with good batteries, make a HUGE difference in cold starting.

 

[JMJNet]

I hang out with the diesel crowd at Truckstop or DieselPlace. I owned 6.5TD.

The best GP recommended is Bosch Duraterms. RockAuto can have it to you shipped for around $8 each. There is also a 5% discount code at the BITOG deals/sales section. There is some quirks on the 6.2 GP controller for some early years but I don't remember what that is. Most people does do the override. You can probably find those override how-to in one of the diesel forum mentioned above. Bosch GP will endure the override. ACDelco 60G comes in second. Never buy the WAP or Autolite which does not last even in California weather.

As for oil, any diesel rated oil should be good for you. It can be Mobil Delvac, Chevron Delo, Shell Rotella, etc, or you can even go Synthetic. You can just go to Wally and get their cheapest diesel oil. In TX, Mobil Delvac (Dino) 15W-40 runs for $9 per gallon at Wally. Great oil. It also have B2G1F deal after rebate. You probably needs close to 2 gallons.