which oil grade?

offpiste · Post by **offpiste** » Wed Apr 02, 2003 11:00 am

It seems as though I'm here to ask as many dumb questions as I can... This one has to do with which grade of oil to use, now that spring is in the air (between the snowflakes). I've been using aeroshell 15 - 50 throughout the frigid winter, and wondering what others recommend as it gets above 50 degrees? Any need to change again at even higher air temps in the heat of the summer?

Around the airport, I get a bewildering array of responses to this question, ranging from "stay with the 15-50 in the summer" to "don't ever use that synthetic crap". Any 170 savvy advice is welcome.

Dave Clark · Post by **Dave Clark** » Wed Apr 02, 2003 1:48 pm

Having just been to a one hour lecture by an Exxon fellow about oils I can say that if you've been using 15/50 Aeroshell then keep using it. It will be very good in the Summer as well and has some antirust agents in it that the Aeroshell 50 doesn't have. Apparantly the Aeroshell 50plus is supposed to have those agents but the Exxon testing didn't detect it. The Exxon semi synthetic multiweight oil looks to be superior to the Aeroshell 15/50 but of course the presentation might have been biased.

Because my Lycoming has been running Aeroshell 15/50 for 1100 hours that's what I'm sticking with year round. Here in Arizona before we leave for Puget Sound in May we could take off on a chilly (40 F.) morning and end up flying in the afternoon out of Phoenix at 95+ degrees. It makes the 15/50 perfect.

zero.one.victor · Post by **zero.one.victor** » Wed Apr 02, 2003 5:31 pm

I like the Phillips XC20-50 for a multigrade.It's not semi-synthetic,it's all natural,man! Quite a bit cheaper than Aeroshell 15-50 too,not much more money than straight Aeroshell W80 or W100. I use it year-round here in the pacific northwest,but if I lived where it got really hot I'd probably run W100 in the summer. From what I understand,the multigrades are a thin oil with thickening agents added--in hot climates I wouldn't need the 20-weight aspect but I would like all the 50-weight aspect I can get.

Eric

Post by **GAHorn** » Thu Apr 03, 2003 9:13 pm

Eric is correct. Multigrade oils are really lightweight oils with additives to make them behave like higher grades (weights) when they heat up. As long as the additive package is intact (not evaporated/degraded) it works fine. But it still drains off the internal parts like lightweight oil, and it is more prone to leaking (like the lightweights it really is.) The anti-wear additives have also been shown to leach copper out of your bearings.
My opinion (What? Horn has an opinion?

) is to use SAE 40 (grade 80) and pre-heat in winter temps below 40F and SAE 50 (grade 100) in summer and temps above 40F. If you can't pre-heat in winter then the multigrades are the best solution. (The reason I don't prefer multigrades is that their additives attack copper bearings when new, and then they deteriorate after a few hours of operation. This is observable when you notice that immediately after an oil change that your oil consumption drops. Then about 20 hours later your oil consumption increases because the additive package is gone and the lightweight base-stock is easily consumed past rings and valves and blown out the vents as mist.) The most common, and therefore least expensive brand of oil when purchased from distributors by the case, is AeroShell in most parts of the country. If I'm out on the road and need to buy a quart, it's most likely the brand available. (Should you believe in not mixing oil brands,...a whole 'nother conversation.)

offpiste · Post by **offpiste** » Sat Apr 05, 2003 12:14 pm

Thanks for all the advice. I didn't know much about anything with these oils, so the insight helps. It sounds like I really can't go too wrong if I keep up with the oil changes. I did notice the phenomenon of increased use of oil about 25 hours after the last oil change, as well as an increase in faint oil staining under the belly. Now I know why.

Given that our temperatures fluctuate so much this time of year, I'll probably stick with the 15-50 until summer actually arrives. Thanks again.

Bill Venohr · Post by **Bill Venohr** » Sat Apr 05, 2003 9:01 pm

When I bought my 170 3 years ago it had been flying with Aeroshell 15W50. After advice from this group, I switched over to straight weight Aeroshell, 40 in the winter and 50 in the summer. My engine runs hot, and I've taken to 50 year round, with good heating prior to starting during the cold months. My oil consumption went down with the single weight oil and I've since installed an oil filter.