Hello all,


I'll be a new truck owner in a month,or so ('05 GMC 2500HD DMAX), and I have always used synthetic engine oil in my vehicles. (mostly because I am too forgetful to change the oil every 3k) I have done quite a bit of reading on the GM website and others, looking for makers of API CI-4 SYNTHETIC oil.


What brands do you know of which meet these specs? Has anyone compiled a list of oil companies who meet this criteria?


Final question for you GM Techs- Do you rely on the OIL LIFE system as it is designed (up to 10k between oil changes, based on driving habits, etc.)? If you say to change the oil every 3k miles, then I'd say you run a shop, because that's what my bosses preach!!!


Ed

Congrats on the new truck.


With regard to oil, Mobil Delvac 1 is what I use. A fully synthetic group IV basestock oil. Among synthetics, it is a popular brand on among forum members.


Up until several months ago, this oil was only available at a few truck stop and Mobil Oil distributors. It was meant for commercial truckers. Mobil just came out with a consumer packaged version of the oil called Mobil 1 Truck and SUV. You should start to see it appearing at stores.


I use the following website for detailed oil information:


http://theoildrop.server101.com/ubb/ultimatebb.php





Personally, I change my own oil and do so when I have the time to fit it in (a very busy business life). This usually works out to a 5k - 7k mileage interval. I don't pay much attention to the oil life indicator.Edited by: OC_DMAX

I use Amsoil synthetic diesel and haven't had any problems. Get a fumoto valve and the oil changes will be much easier. I change the oil at 10,000 miles but the filter gets changed every 5000 miles. Remember, the oil is needed, but we have to filter out the bad stuff. Just don't use Fram oil filters!

Thanx guys,


I've read-up on the Amsoil, and just got back from the Mobil website. I guess my next questions are:


What's the difference between "Mobil 1 Truck and SUV" & "Delvac 1" They are advertised in the same ways by Mobil, on two different web pages. Is it the same but just a difference in packaging? Any ideas why they don't offer a synthetic 15w-40 (GM specs)?


...and what's a fumoto valve ???


Ed

Why would you want a 15w-40 when you can have a 5w-40?

Fumoto valve replaces the drain plug. OIl drain is done by opening valve. Fumoto offers 2 setups, one w/ a nipple , the other w/o. Get the one w/ the nipple, that way you can slip a hose over the nipple and drain your oil into pan or old oil bottles for easier disposal.

What's the difference between "Mobil 1 Truck and SUV" & "Delvac 1" They are advertised in the same ways by Mobil, on two different web pages. Is it the same but just a difference in packaging? Any ideas why they don't offer a synthetic 15w-40 (GM specs)?


I looked at the spec sheets several months ago. I could not see any difference.


On the website I referenced above, several people have submitted samples of the Truck and SUV oil for analysis. If I remember correctly, there was a slight difference in the Boron levels (relative to Delvac 1), but everything else looked identical.


Other than that, it is just the convenience factor. You can get Mobil 1 Truck and SUV at the local auto part store in quart bottles, while the Delvac 1 usually must be purchased in gallon containers from a Mobil Oil distributor.


One comment with respect to Amsoil Oil, I do not believe it is certified to the CI-4 standard. (the key word here being certified - bold and underlined).

Why would you want a 15w-40 when you can have a 5w-40?





Burner,


As a Technician I have 24 years under my belt, a few tools , and access to some really great technical info.


As a chemical engineer I have no experience, no equipment, and no knowledge.


Why would I want a 5W-40 when GM says to use 15W-40???


Ed

5w-40 OR 15w-40 They are both still 40 weight oils. The only difference is when it gets cold the 5W-40 will pour a little easier.


Amsoil at $15 a gallon or Delvac at $20 plus a gallon.





Greg

Greg correct me if I am wrong but Amsoil was the First on the market and the most coppied by the majors.


Geno

5w-40 OR 15w-40 They are both still 40 weight oils...





I don't mean to sound dumb, but if it as simple as that, then why does GM say to NEVER USE 10W-40 in the Duramax ???


I can understand some of you northern dwellers wanting 5W-30 for the winter benefits, but here the winters are rarely below 20 deg F, and the summers are swelteringly hot.


Ed

Amsoil, often copied, never duplicated......when only the finest is needed...they offer many products...I've found the Marine oil, 10W40 to be the best economy and protection, but they offer other formulations...look into bypass, 1 micron filtration also, not to extend life of oil as much as to just keep oil cleaner!





w1ngsmk

I don't mean to sound dumb, but if it as simple as that, then why does GM say to NEVER USE 10W-40 in the Duramax ???


I can understand some of you northern dwellers wanting 5W-30 for the winter benefits, but here the winters are rarely below 20 deg F, and the summers are swelteringly hot.

If you take a look at the chart on page 5-something in the diesel handbook you will see that the 5W-40 covers the same high temperatures as the 15W-40 but extends to a lower temperature. I use Rotella-T 5W-40 synthetic and see no difference on my oil pressure gauge, even when it is 95+ outside.

Is it 10W-40 that GM says not to use? I forget, but it might be 10W-30. There was also a grade shown in the middle (10W-40?) that had a very limited temperature range. With the exception of the lower temperature, I don't see anything that says I can not use 5W-40 year around.

Jim

Thanks, Jim for the opinion, Its the best reasoning I've heard yet. I don't yet have the truck or consequentially the owners manual, but the online version failed to make that aspect clear.


BTW, it is the 10W-40 which is prohibited, and the 10W-30 which should only be used in a pinch. (according to them...)


Thanks, ALL for your opinions,


Ed

5w-40 will have more additives to increase the temperature spread than 15w-40. The increased additives means less base stock, and less lubrication.

Amric, define base stock on C-4 & C-5 oil.


Thanks

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.


Multi viscosity oils are one of the great improvements in oils, but they should be chosen wisely. Always use a multi grade with the narrowest span of viscosity that is appropriate for the temperatures you are going to encounter. In the winter base your decision on the lowest temperature you will encounter, in the summer, the highest temperature you expect. The polymers can shear and burn forming deposits that can cause ring sticking and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that range. This has caused problems in diesel engines, but fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content. It is the oil that lubricates, not the additives. Oils that can do their job with the fewest additives are the best.

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.


Multi viscosity oils are one of the great improvements in oils, but they should be chosen wisely. Always use a multi grade with the narrowest span of viscosity that is appropriate for the temperatures you are going to encounter. In the winter base your decision on the lowest temperature you will encounter, in the summer, the highest temperature you expect. The polymers can shear and burn forming deposits that can cause ring sticking and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that range. This has caused problems in diesel engines, but fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content. It is the oil that lubricates, not the additives. Oils that can do their job with the fewest additives are the best.

Wish it were so simple. With a 10K drain interval you can be changing oil in summer that will be in the engine during the dead of winter and visa versa. So if you go by the end if the cycle you can be completely wrong for the current and near term.

Jim