Swiching from Synthetic oil to normal OK?

[iggman]

A friend tells me it's bad to switch back and forth between normal and synthetic oils. Any truth to this?

I use synthetic in the winter months only due to it's improved flow when really cold. Otherwise normal oil.

[CREWZIN]

I couldn't really say if it might be bad for yor engine, but why not save yourself the hassle and switch to a Synthetic Blend. There's a couple of name brands like Castrol and Penzoil that make a blend and you could just switch to a lower grade (5W30) in winter and higher grade in summer.

[iggman]

I don't know enough about blends. I use 5W-30 year round bc the owner's manual says to.

[Gman]

iggman,

The blends/Grades; 5w30,0w30,10w40 etc... are the weights of the oils at different tempatures. For example in colder weather you want an oil that flows at real cold temps you would use the 0w30. In hotter weather you would use a 10w40. The reason the weights are getting thinner is also because the tolerances in newer engines are tighter. So the oil doesn't need to be thicker in order to provide that film protection on your cylinders, cams and bearings and inside your engine it needs to flow better with those tighter tolerances the manufactures make. As far as mixing the synthetic with petroleum base it won't hurt any thing at all. But like crewzin said. Why switch back and forth. You could just change the Grade of synthetic to meet your tempeture conditions. NOW if your running a turbo that is bad. Even if you change brands you can sometimes lose your turbo bearing. Grades are okay though. Now brands are also significant as to where they come from, ie some have a high sulfer content; Penzoil, Kendall, Quaker State mostly from the Northeast. Then you have a Texas grade like Havoline, Chevron, Mobile, these have a lower sulfer content (Don't get dirty as fast basically). I have done my research and the web can help you allot with info too.

Gman

[jl.warren]

I'm not sure why you want to shift back to regular oil if you've changed to synthetic. I changed my '01 PT Limited to synthetic at 3,000 miles and wouldn't dream of using anything else (better gas economy (26 mpg (EPA) to 31 mpg- I have a manual transmission) and less wear on the engine (as verified by oil analysis)). I've changed the transaxle fluid to a synthetic one as well, but I haven't done a long trip again to recheck the gas mileage yet. (The first time was after a trip from San Diego, CA to Santa Barbara last September. The following week I went to an AAA car fair in L.A. and verified that my odometer was reading accurately.) If you switch back and forth, you are probably going to negate the effects of a good synthetic because of the extra wear occuring when using the petro oil. Then all you'll do is burn more expensive oil. Even if you've changed your oil per the "B" series in the shop manual (every 3,000 miles), it is probably too late (due to the increased wear occuring when using the petro oil) if you have much beyond 25,000 miles on the PT.)
I've been using synthetic lubes for over 17 years and I won't use anything else. The difference in oil costs is more than made up by gas savings, and wear and tear on your engine/drivetrain. J.L. Warren La Mesa, CA

[iggman]

My mpg went unchanged using either oil.

[jl.warren]

quote:
My mpg went unchanged using either oil.

That's interesting! Which oils were you using? And, what oil filters?

What kind of car are you discussing here? (engine size/transmission type (auto/man)/mileage on the car at the time of switching over to the synthetic lubes-NOTE: this is of HUGE importance! If you switched to synthetic after about 25,000 miles (a rough rule of thumb), I would totally agree that you are RIGHT in your mpg not changing. That's because significant wear has ALREADY occured in the rings, etc., and the synthetic oil can't undo that. Based on lube oil analysis, the wear that synthetics minimize occurs primarily in the first couple of oil changes (3,000-15,000 miles) from the car being new. That's why I have always changed my cars over to syn-lubes within the first couple of factory oil change periods (normally 3,000-9,000 miles). Also, switching back and forth between petro and syn lubes (discussed in an earlier post by someone else) is a waste of time (and money); pick one or the other (petro or syn) and stay with it! Otherwise, within a short span (25,000-30,000 miles) the wear, while using the petro lubes, wipes out the ability of the syn lubes to keep clearances to a minimum, and therefore leakages to a minimum, and wipes out the syn-lube's ability to minimize wear and keep your gas mileage as high as possible.)

Every time I've switched one of my cars (1984 Jeep Cherokee, 1986 Dodge Caravan, 1999 Dodge Caravan, and now my 2001 PT Limited) to synthetic (after the initial breakin period (usually about 3,000 miles), I have ALWAYS seen at least a 3-4 mpg increase (especially in highway driving). Admittedly, automatics don't show as much an increase due to the transmission's losses (between 25-35% as compared to a manual transmission, that's why the EPA for an automatic is less than the EPA for a manual tranmission.), but my Dodge Caravan (3.3L) got about 27-28 mpg as compared to the EPA (24 mpg). (The ONLY reason I got rid of my 1984 Jeep was because it had a carburator, and it was becoming too hard to find someone that really knew how to tune it up. It was getting between 27-29 mpg when I turned it in for recycling) I also use lube oil analysis to see what my wear rate is, and to verify that the oil is still doing its job. I make my oil (and filter) changes based on the oil analysis. While under the new car warrantee, to keep DC happy, I sample every 3,000 miles. Now that my car is "out of warrantee (35,000 miles)" I'll switch to 5,000 mile samples. The analysis is about $20, but only takes about 10 minutes to do (and I don't have to get under the car, or change clothes to do it!) It costs $1.70 to mail off, and it comes back in a week. I had more, but I guess I've talked too long. Sorry. JL Warren[u]</u>