therewolf

It's been 10-1/2 months, and synthetic oil is starting to make a believer out of one of their worst skeptics.(me) My intention when I first started was to eliminate the 3K oil change from my maintenance schedule, to cut down on redundant labor, and hopefully, to reduce my overall costs. Mission accomplished.

11.5K after the first synthetic oil change, the oil I drained from my truck seemed very capable of easily sustaining more mileage than I put upon it. I also didn't get the pressure "drop" which you get from most natural oils at @4K at my gauge.

I had to reset the OLM on my 2500HD DIC at least 3 times, but it apparently doesn't measure ACTUAL oil breakdown, it only calculates the life of non-synthetic oil in your system.

My paradigm for this test is AMSOIL 0-W30,(at a not unreasonable 10$ per quart, considering it's longevity) and K&N Oil Filters. I particularly like the K&N filter design, which allows you to tighten and loosen it with a crescent wrench.

I intended to change the oil filter at @ 6K, but life and bad weather interfered, so my first filter change was at 7.5 K.

As to economy, I calculate my natural oil changes expenses, with the protection of a cheaper filter, at @42$ per 3000 miles. The cost of the synthetic oil change, even with the more expensive K&N filters, came to @25$ per 3000 miles.

At this point I intend to go to 15K between oil changes, with a filter change at every 6K. My eventual goal will be to see if the synthetic oil can make a successful interval of 18K, which will not only decrease labor further, but also decrease the expense of oil changes to less than 20$ per 3000 miles.

nauticstar87

Awesome write-up Therewolf. I still change mine a 5-6k. But my truck also hits 5500RPMs a lot more than yours probably... LOL. I am going to switch to K&N Oil filters next change.

therewolf

Thanks, nauticastar.

You're right,I almost NEVER see 5500RPM. I replaced my more aggressive gearing, and do a lot of highway mileage. With 342s and the lower revs they reward me with at higher speeds. Bear also in mind I'm using a 6.0Vortec, with 4L80e transmission, so I get all the power I need at lower revs, for the most part.

I can't say yet with absolute conviction that synthetic oil is for everybody. Especially if you don't take the extended drain interval. Then you would be paying 2 or 3 times what you pay now for an oil change. You have to be especially careful with your maintenance if you do high RPMs. It's been my experience they tear up valve train components.

I've also put AMSOIL synthetic, with a Wix element type oil filter in my daughter's Saturn ION with the 2.2L engine and automatic transmission. Next year sometime I will be including her vehicle in the update, for the purpose of addressing smaller engines.

brod4343

Hi Therewolf. Did you happen to notice any increase in gas mileage with the synthetic oil? A friend of mine running the gas engine said he increased his mileage 4mpg with Mobil 1.
Thx

2wd-K5

i got as big jump when i did in my jeep, a 91 cherokee changed it all to sythetics (was a mistake just for the extra leakage that went on wiith it) other than the leakage my mpg went up 3mpg and much more usable power, everything just seemed smoother, i would sugest only in newer vehicles under 10 years old, old gaskets let for more seepage

brod4343

Have any of you guys heard anything regarding the use of synthetics in the Duramax, specifically gas mileage?

therewolf

Hi brod4303,2wd-K5,

How are you guys doing today.

I haven't seen a noticeable or countable increase in mileage. The engine runs a little quieter, and oil pressure is @ 10% better than with Dino oil.

I'm guessing the mileage increase seen with smaller, more aerodynamic vehicles is lost on my brick-shaped,7100LB. behemoth.

As to whether Mobil1 oil gives improved gas economy, I can't honestly say. I don't have any experience with Mobil1, but I can say the brand does have a lot of loyal followers.

Z15

I am using the AMSOIL 0W-30 in my 2009 CTS for about 12,000 miles now. Prior to that I had it in my 2005 CTS, my 2002 Trans AM. I only change the oil once a year on all my vehicles, last time was back in Oct 09. The CTS came factory filled with Mobil 1 but that was gone by 3,000 miles. The dealer gave me a free oil change so I brought in the AMSOIL 0W-30 and asked them to put that in instead of the free Mobil 1. They did along with a free AC Delco filter.

I did notice when I had the drive train fluids changed over to AMSOIL synthetic (its all wheel drive with G80 limited slip rear axle) that my mpg went up 0.3 mpg to 23.7mpg. I know that's not much but its an improvement. Also the little but of chatter I used to get turning corners has disappeared.

I just changed my new 2010 GMC to the 0W-30 at 1,000 miles. Going to change all the other fluids soon, both axle, trans case and transmission.

I have used AMSOIL for many years, over 20 for sure.

I also have a 1993 Chevy Lumina here that was my mothers car new. She does not drive anymore (90yo) but I am keeping the car till it rusts away. I converted the engine and trans over to AMSOIL about Jan of 1993 (she bought car new in Aug of 92). The car is just shy of 100,000 miles as she only went to church and to the store with it, I got it with 60,000 mi back in 2006. I would only change the oil once a year no matter the miles she drove it. Today the engine runs perfectly and so do the trans. I use the car in the winter and park the CTS. I have to laugh as the GM service manager warned my back in 1993 that I would ruin the engine putting in the synthetic oil and he really did not want to do it but I insisted.

therewolf

Hi Z15,

Welcome to the Chevy Forums.

.3 MPG is a very valid improvement, believe it or not. Most mileage improvements are cumulative, coming very piecemeal. Of course, they all add up. What the improved mileage doesn't readily show is increased system efficiency, which is almost priceless.

Having a full-size truck is perhaps all the more reason to be looking for increased fuel economy. IMO, any one mod which brings more than 1MPG improvement is a quantum leap in gas economy.

I used Amsoil tranny fluid during my last filter change, but I haven't changed all my fluids to synthetic yet. My differential fluid change is next summer, so I'm considering the changeover then, as most of my fluids will be syn at that point anyway.

But so far so good. While i don't intend to change brands, or try them all, I have noticed fierce loyalty to Mobil1 by many, which is a hallmark sign of good quality. Others also like Royal Purple Synthetic.

2wd-K5

i noticed with the diferential fluids was what gave me the noticable improvement in power, seemed lees of a struggle, but keep in mind, cherokee axles werent the best at keeping their fluids and it needed to be topped up every oil change