[Aufgeblassen]

It is indeed true. I switched to Synthetic Oil (Delvac 1), and fully expected to change it every 60,000 miles, changing the fuel filters every 30,000 miles.

At 30,000 miles, I changed the oil filters (3 of them on my Volvo engine), and had oil analyzed. It looked good. So I checked the oil (i.e. analysis) at 60,000 miles, and it looked nearly identical. So I checked it @ 90,000, and it looked pretty much the same. So I skipped an analysis @ 120,000 miles, and checked again @ 150,000, which said I should change it, and I did.

BTW: Mobil 1 (5W-40) Heavy Duty Turbo Diesel Truck Oil from Wal Mart is A LOT cheaper than Delvac 1 from a truck stop, and is virtually Identical. I use it when changing oil filters, because I need to add a full 2 gallons of top-off oil.

Note: My truck has approx. 1,066,000 miles, and burns as little oil as when I got it at 538,000 miles, some 5 years ago.

[YerDaddy]

You put in 8 gallons of fresh oil during that time (2 gals. at each filter change) so it wasn't the same 10 gallons that started out in the crankcase.

Just sayin'.......







So you got a bypass filter or what? What brand filters you buy?

[Musicman]

Originally Posted by YerDaddy

You put in 8 gallons of fresh oil during that time (2 gals. at each filter change) so it wasn't the same 10 gallons that started out in the crankcase.

Not to mention the oil that was lost due to engine consumption, but it's still a heck of a lot cheaper to do an oil analysis and replace an oil filter at regular intervals and only replace the oil when analysis indicates it is required. Some people on here say they do a full oil and filter change every 15k miles, which even if you’re doing it yourself, using cheap oil and buying bulk would cost many thousands more over the life of the truck than using the OP’s method. In my ’03 C15, I could easily go as much as 90k miles with no oil change. With my ’06 ISX (EGR disconnected) I’m able to go 60k on dino oil and recently switched to a full synthetic (which gave an improvement on fuel economy I might add) and expect to be able to leave it in at least 120k miles. As long as you religiously pull samples and use a reputable lab, this is a smart, money saving method.

[Aufgeblassen]

Originally Posted by Musicman

As long as you religiously pull samples and use a reputable lab, this is a smart, money saving method.

Indeed. Checking oil every 30,000 miles @ Speedco for around $15 is no big deal at all.

[heavyhaulerss]

I may try synthetic oil. I have always changed my oil at 10,000 miles. just the look of the oil at that many miles, makes me want to change it. I really don't want to wait til oil analyst tells me it need's to be changes, by that time, i.m.o it should have been done already. I know what mfr's reccommend, but it is not in their interest for every one to get a mil miles out of their engine, without any major work. with me, it's probably, old habits die hard. after over 1.3 mil I attribute that to my maitenence, preventative & otherwise. when I look at my oil drain out with 10,000 miles on it compared to when it is new, I think no way is this old oil anywhere near as good at protecting my engine as clean notor oil. the gear train, turbo, & so much more depend on sufficient clean oil. since I had my inframe done & now the engine in broke in, I wil give synthetic a try. I hope it works well. I have heard it does well especially in winter months. I alway's had good luck using lucas oil stabilizer. I know the opposition to it. but after over a decade & 1.3 mil, it certainly did not hurt it. I think it helped. maybe, maybe not. when I do use sythetic, I will post any negative or positive from my experience with it.

[allan5oh]

I take it yours is an older D12? I have a 99 and it is very clean like yours. I just put synthetic in it the first time and we'll see how long it can go.

I do have a bypass filter, making it 4 oil filters. I did 60,000 mile oil changes before.

[ironeagle_2006]

This is coming from an old Millis Driver. We ran Bypass filters in 98 and ran Mobil 1 Synethic then. We went 300K between Oil chnges with an Oil analysis every 50K Trucks had Auto Greasers on them. Now at Henderson we ran Some Special Hydro cracked oil by Conoco and were going 100K on the oil with Bypass Filters. Never had any oil issues there. Millis on the other hand was always having Turbos fail but then when your pulling 80K in Beer with 350HP all the time with trucks geared with 3.33 rears you will have issues.

[heavyhaulerss]

I have 350/365 h.p. & always pulling right at 80,000 still original turbo. all other components related to oil have shown the benifit of keeping oil changed. as far as when to change, I guess it could vary. what & when do contaminents get in the oil? in real cold temps & especially ideling for long periods of time, I think changing oil sooner than you normally would is good for your engine.

[Copperhead]

That is what your oil sample will tell you.... how much soot you have, how low the additive package is getting, what the wear numbers are, etc.

So it would vary based on the various conditions you mentioned. You would get more or less time on the oil before it needed changing.

Myself, I never got into the seeing how long I could go game. I have done 25,000 to 30,000 mile oil changes since mid 90's with no oil related problems. Kinda got stuck in that oil change cycle. But, I have to admit, my oil samples come back stating that oil is good to run further.

I understand the idea that changing oil sooner is better for the engine. But using that logic, why not change the oil every week? If the oil samples show the oil is still good and the contaminates are not a problem, then I guess you could safely go as long as some have mentioned. I guess I fall in the middle on this one. I go a lot longer than a lot of people do, but do not go for the real extended drains like others do. I have no real argument against going longer. The oil samples say I can. Maybe one day I will make a real attempt to see how long I can go.

You do have to watch a lot of factors on what the oil is doing to make an informed decision. I would not rely only on a lab to tell me. Is the viscosity thinning or thickening and at what rate? Do the wear metals rise gradually, and then spike at a certain point even though they are still within limits? Is there a gradual drop in TBN (additive package) and then it drops more quickly, even though it is still in limits? Was that sudden spike in lead count due to a bearing or just from using a fuel additive like Power Service during a cold snap? Is the silicon (dirt) staying fairly level and then it spikes, indicating the air filter needs changed out? For one to make a truly informed decision, it is advisable to do a lot of reading on how to analyze the various results in an oil sample and it takes several samples on an engine to start to see patterns that can help in determining the proper oil change interval. Not a hard thing to learn, but I won't rely only on a lab recommendation. It is only the informed opinion of the tech that tests the sample and it is not their money on the line.

For me, after looking at samples on my engines for a decade and a half, my comfort zone has come in at 25,000 to 30,000 mile average oil change intervals, but that might vary if I was running different engines than Cummins I have had. I have seen times when, due to various conditions, that time frame was pretty close, then other times I could go longer. It has worked for me since I have never had to open up an engine before it was time to do a rebuild. Maybe just dumb luck, but I have never done a rod and main bearing job on an engine before rebuild time, never lost a turbo (did lose an actuator on the VG turbo on my ISX, but that had nothing to do with oil and didn't need to replace turbo), and got 1.4 million out of my last engine and still hadn't gotten opened up and still ran pretty good (should have kept it and put it in a glider kit truck). My ISX now has approx 593,000 on it and haven't had any of the bearing and cam issues that others have had. Wear metals on the ISX still are low as younger engines.

Tried various full synthetic oils, but got wear metal spikes that concerned me. Finally settled in an inexpensive 40% synthetic blend that give me real good wear numbers and is very stable over my normal oil change intervals. If some can get and are comfortable with real high mileages between oil changes, cool. Each engine make and model will be different as is the operating conditions that it is run in and you have to find what is right for that engine. For instance, I cannot really see a dump truck operating in and out of gravel quarries going 100,000 to 150,000 on an oil change, even with a bypass filter. But an OTR truck that runs consistent routes with consistent loads could probably go to almost unheard of distances before actually needing to change the oil. Most of us fall somewhere in the middle and would have to determine the proper interval based on our individual operation.

[YerDaddy]

All you guys worry yourself bald about oil and samples and miles and filters but... how many of you have made your own prelube system like me to fill the oil galleys with oil at positive pressure before cranking the engine?
Synthetic or dino when you crank that engine with zero oil pressure you are giving it the most wear it will have all day.