Just interesting in your opinions about using synthetic oil in engine.In my VN670 with 16 liter volvo engine I use Delvac fully synthetic oil since new.Change interval 50000 miles(according to manual using mineral oil change interval 25000 miles)Hope to see your comments soon guys.

My buddy also uses Delvac 1 in his truck, I think he said he changes oil around 60-75k, but changes the filters at 15-20k.
All the research I've read seems to suggest that you can use regular oil during the mild weather months (spring and fall) and use syn during the rest of the year, since syn oil's increased resistance to temperature extremes helps the most then. But of course, using it all year round won't hurt anything, and should help keep your engine cleaner (on the inside).

In my opinion Synthetic lubricant products are well worth the money for simply the extended change interval alone, not to mention the possible improvements in fuel economy and better protection for your equipment.

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I use Amsoil's Heavy Duty Diesel full synthetic, and also use Amsoil throughout my truck for the transmission and axles. This is on a 2000 Volvo with Cummins N14.

When I first bought the truck, it came with what I'm sure was conventional oil. After switching, I immediately noticed that my truck was running cooler on hills. Where the fan would kick on at the top of the hill before, the temp wasn't even getting close to that.

Fuel economy also started to climb. I was getting an average of about 6.1-6.3, and now I post 7-7.5 pretty steady.

I have always used synthetics in my vehicles. After seeing a dyno test done by a Mustang publication years ago, it really changed my mind. The test Mustang actually got 5 extra hp at the rear wheels! Add to that the extended drain intervals, and it's a no brainer.

I definitely agree with the intervals and also the mileage, I was barely hitting 5.5 with the oil in my truck when I bought it (bought an '01 Columbia Daycab earlier this year). AFter having the engine flushed and putting in Amsoil 15w40, I"m now getting well above 6.5, on the exact same run in the same temperatures.
ANother thing is the TBN number which the higher the better, and makes it last longer too.

For the price diff between amsoil and other oils, I just use the amsoil on everything, from my cars to truck to lawnmower.

On the Cummins website they say that their research does not recommend fully synthetic oils, I wonder why that is since they have to cover warranties on their motors so if it was better for it you would think they would recommend it.

Hmm, not all engines are the same maybe?
Mazda for example specifically says NOT to use synthetic oil in the new RX8s, while they recommend synthetic (of course not required) in the rest of their line of vehicles for optimum performance.

As for warranty, if you go extended intervals, some manufacturers will still try to deny, hell I"ve had a manufacturer try to deny my engine warranty even though I did REGULAR intervals. Getting the warranty is easy, getting them to honor it is another story.

Also, I jsut checked Cummins' site, can you direct me to the link where they say they dont recommend fully synthetic oils? I might have overlooked it.

Edit: I found the link using a GOogle search and I'd still like to see what you were referring to, as this actually condones Synthetic, except for the first oil change.
cummins*dot*com*slash*jp/pages/en/customerassistance/faq/answers*DOT*cfm?uuid=000B1F97-EDC2-1981-9BB380C4A8F0FC10

Can you mix synthetic oil with conventional oil?

Yes you can, look at your average auto parts store: all the synthetic blends are exactly that, usually half syn and half conventional. The only caution to this comes from the oil companies themselves, they recommend that you stick with the same brand of syn and conventional (eg, Delvac 1 and Delvac).

RX8 is a rotary or wankel motor....so it is a different game....


ALL TRUCKS WILL RUN BETTER WITH SYNTHETIC!.....

Synthetic is superior to conventional, maybe cummings does not want to get an extra 500k out of a motor so they can sell parts to re manufacture them...


K