5W40 synthetic diesel engine oil in a modern gasoline engine?

[clemsonfor]

Thats assuming the same engine size. I would think a large displacement V8 would generate more soot than a tiny four cylinder in an economy car thus negating the dilution effect of a larger sump.

My Kenworth has a 10.8 liter engine and holds 44 quarts. My wife's car has 3.5 liter engine and holds 5 quarts. The Kenworth has three times the displacement but holds nearly 9 times as much oil. Maybe that is why the big rigs have the longer oil change intervals because the displacement to oil capacity ratio.

i was going to say the similar. A 4 cylinder ford focus is burining maybe a third of the fuel to go that 10K miles that that large v8 tundra is going so even though there is more oil its got more fuel run through the motor on said oil which can lead to more contaminets. Just my thinking.

 

[Soundguy]

Thats assuming the same engine size. I would think a large displacement V8 would generate more soot than a tiny four cylinder in an economy car thus negating the dilution effect of a larger sump.

My Kenworth has a 10.8 liter engine and holds 44 quarts. My wife's car has 3.5 liter engine and holds 5 quarts. The Kenworth has three times the displacement but holds nearly 9 times as much oil. Maybe that is why the big rigs have the longer oil change intervals because the displacement to oil capacity ratio.

I agree.. my diesel pickups essentially hold 4 gallons ( ok, about 15.5 qts for the nit pickers ).. vs my wifes gas van. 'normal' 5-6 qts. with engine sizes on the diesel 7.3 - 6 vs 5.4 gas. you also see that disparity on displacement to capacity. a little more displacement ( up to 1.5, but , but capacity 2.75+

 

[Copperhead]

How long an oil will go is dependent on many factors. Sure, sump capacity plays into it, but also the quality of the motor oil and the additive package that is a part of it is the largest determinate of how long a oil will hold up. Something like Amsoil's Signature stuff, they have such a high TBN compared to most other motor oils, that it can control acids and such in a motor a little longer. And these computer controlled engines nowadays really can make a difference in how long an oil will last. The OEM stock oil life monitoring systems are pretty darn accurate. Though they don't actually test the oil condition, the algorithms they are set up with take into account the lowest quality oil that meets the OEM specs. So it is not uncommon for average bulk oil like a dealer or lube place would use would last 7000 - 10,000 miles without any issue. A high end quality oil could easily go 15,000 miles in an average motor with a 4-5 qt sump. I take the 6.0L in my pickup, with a 6 qt capacity, to the life of the OLM, which is usually around 7500 miles. A couple of oil samples showed it could go longer, but hey, it is only 6 qts so I keep my comfort zone and change it.

Now true, a larger sump like on a heavy diesel can make a difference as well. My old Detroit 60, which is a factory rebuilt, the OEM recommends 15,000 mile oil changes. After running several oil sample tests, I have it at 25,000 mile oil changes using a 15w40 synthetic blend. Gonna get a little gutsy and do a 10w30 syn blend for the next oil change. My oil supplier has been twisting my leg to try the stuff. The Detroit Lube Manual allows a 10w30 even in the Series 60 motor, so gonna see how it holds up. Will drop the oil change to 20,000 till I get a couple of oil sample reports to see how it is doing.

 

[davesl708]

Thats assuming the same engine size. I would think a large displacement V8 would generate more soot than a tiny four cylinder in an economy car thus negating the dilution effect of a larger sump.

My Kenworth has a 10.8 liter engine and holds 44 quarts. My wife's car has 3.5 liter engine and holds 5 quarts. The Kenworth has three times the displacement but holds nearly 9 times as much oil. Maybe that is why the big rigs have the longer oil change intervals because the displacement to oil capacity ratio.

My old 03 Trailblazer EXT (six cylinder) had a seven quart capacity and the computer calculated an oil change around 10k to 11k. My 04 Suburban has a V8 and has a six quart capacity. The computer calculates an oil change around 10k. My Subaru has a four cylinder with 4.5 quart capacity and recommends 5k change.

 

[sixdogs]

Have been around since the days of the 1,000 mile oil change through today's 10,000 to 25,000 mile oil change, the question that begs is will the day come for oil quality that lasts the life of the vehicle?

I used to never violate the 3,000 mile limit but now I regularly go nearly 10,000 miles in non-severe conditions.

 

[Copperhead]

Probably not on motor oil, simply because of all the outside contaminants getting into the motor and the combustion process. But we are already there and have been for a while on lifetime trans and gear oils. Even commercial trucks have been on 500,000 mile gear lube changes for some time, with 750,000 mile warranties on trans and diffs. Detroit now has a recommended oil change interval on their DD15 heavy diesel of 50,000 miles using basic off the shelf CJ-4 motor oil. In some cases, I loathe some of the technology that gets thrown in our face, but in this case, the advancements that have been made are fantastic.

 

[davesl708]

Probably not on motor oil, simply because of all the outside contaminants getting into the motor and the combustion process. But we are already there and have been for a while on lifetime trans and gear oils. Even commercial trucks have been on 500,000 mile gear lube changes for some time, with 750,000 mile warranties on trans and diffs. Detroit now has a recommended oil change interval on their DD15 heavy diesel of 50,000 miles using basic off the shelf CJ-4 motor oil. In some cases, I loathe some of the technology that gets thrown in our face, but in this case, the advancements that have been made are fantastic.

I think filtration is the key. Filters are much better today than 20 years ago. The oil its self does not brake down. It is the additives that break down and the contaminates in the oil. A perfect filter and additives that do not shear will give us life time oil.

 

[ray66v]

I think filtration is the key. Filters are much better today than 20 years ago. The oil its self does not brake down. It is the additives that break down and the contaminates in the oil. A perfect filter and additives that do not shear will give us life time oil.

Even mineral oil is as good a lubricant, as synthetic oil now, under normal operating temperatures. That is due completely to dramatic improvements in additive technology. Which includes enabling them to last longer.

A good filter will of course help, if there are contaminates. But, any way you cut it, it's still just a filter. It can't stop the oil from crapping out.



From the earlier discussions about oil quantity: I believe larger oil sumps, are more about temperature control than anything else.

 

[arrow]

Speaking of filters, On my 95 Dakota, the filter looks like a piston, size wise. The filter on my Forester is a bit larger than a shot glass. Makes me think residual burn particulates in gas engines are not the issue they used to be. 4 .2 ots in rthe Soob and 5 qts in the Dak.

 

[Copperhead]

I think filtration is the key. Filters are much better today than 20 years ago. The oil its self does not brake down. It is the additives that break down and the contaminates in the oil. A perfect filter and additives that do not shear will give us life time oil.

Significant truth to that idea. While additives can be replenished, it is the viscosity improvers that actually shear and break down. You are correct, the base oil itself doesn't break down. But VI are in a class by themselves compared to additives that control oxidation, soot control, etc and those that act as detergents and such. One can replenish those, but one cannot just replenish viscosity improvers. They are an integral part of the motor oil as it was developed. The only way to make an oil longer lasting in that regard, is to have a base oil that significantly reduces the need for VI. But to do that, even with PAO Group IV synthetics, you greatly restrict the limits of the cold flow. For instance, while there are many PAO full synthetic 30w oils that qualify as 10w30 on their own without any VI, as you go to something like a 5w30 and even further with a 0w30, the use of viscosity improvers is the only way to get to those low cold flow levels.

And filtration or additive replenishment will never compensate for such things a fuel dilution. So either via fuel dilution or VI shearing, once an oil goes out of grade, it has to be changed.