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So, not too long ago I learned that sometime in the past years the term "Full Synthetic" was allowed to be applied to sythetic blend motor oils as long as the base stock is from something around 60%-70% synthetic base stocks. This applies to all the common mass-market "synthetics" including Castrol, Mobil, Penzoil, etc.

This fact sheds some light onto why botique oils like Redline, Royal Purple, and Amsoil can justify their exorbitant prices and claims of far superiority over other "full synthetic" oils. I learned that some of the Amsoil formulations don't even adhere to the API standards so they can provide better lubrication without heavy-handed regulations that cater to the EPA more than the life of customers' engines. For the first time I wondered if I was really doing my car any favors by sticking with Mobil-1.

So last month I switched from my normal Mobil-1 "Full Synthetic" 10W-30 to the Amsoil SS 10W-30, along with Amsoil's Ea filter. For the most part there's no percievable difference... until I ran an Auto-X with it. It used to be that during the last couple of runs of the day, my car's engine would be extremely hot and the valves would be noisy and clacky and it would sound like an old Ecotec with a loose timing chain. I always attributed this to the engine being 18 years old with 160,000 miles, and inevitable during these types of events.

However with the Amsoil, that never happened! 6 runs and the car ran as quietly after the last as it did before the first. The noise I was hearing definitely had to be attributed to the Mobil-1 loosing viscosity as the temps climbed.

So yeah, if you do any kind of competitive driving on a semi-regular basis, I'd definitely recommend switching to one of the way too expensive oils. I also plan on taking Amsoil up on their extended drain intervals, since it costs damn near $10 a quart and I'm not doing a chance every 5,000 miles "to be safe" if there's no benefit there. I figure at the 10,000 mile mark I'll send in a sample for analysis to see if it's safe to push to the full 25,000 miles (with a filter change at 15,000).

If you never do more than spirited back-road runs and parking lot fun though, or only do an auto-x/track day a couple of times a year, I would say this is probably a waste of money as even the "sorta fully synthetic" oils are still plenty good for regular driving.

I ran amsoil in my first subaru that I was only driving in winter time so I wouldn't have to worry about changing it but once a year. Then the car was sold to my sister who ran it for probably 3 years without changin it and something like 35-40k miles. I found this out when I changed her oil last year and found the same amsoil filter on the engine and asked her if she had ever changed it. Of course not. So that oil was probably used for 45-50k miles haha. No problems. Engine still runs great.

Have you had the Amsoil in the car long enough to do some fuel mileage comparisons to the Mobil 1?

Yes, and no I haven't seen any fuel economy difference. But I'm also a stoplight hero, so my mileage just sucks all the time regardless.

I do wanna say the car seems a tad more responsive, but I generally don't listen to my butt dyno unless actual power-adders have gone on the car. Its also hard to tell for sure because after the AWIC install my car has been super-sensitive to the temperature/humidity, so unless I do back to back assessments the same day I really can't say with any confidence.

James, first of all, I really appreciate your review of the AMSOIL. The AMSOIL did well when I ran it in my '81 dual-range GL-10. Then, when I put the AMSOIL gear oil in my tranny and rear diff combined with the engine AMSOIL, I gained a real 1.5 mpg or better as a side benefit. I had no problems with the engine (or the rest of the car, for that matter) for 224,000 miles when I sold it to a friend who really wanted to buy my Suby.

In my ss, the Mobil 1 synthetic always seemed just so-so to me. Yes, it's a different engine but the Mobil 1 still never really impressed me. Oh, it was better than dino oil but it just didn't seem it was outstandingly better. The 110-120 degree summer heat in AZ was probably hard on the engine between air intake temps and engine bay ambient temps. But the Mobil 1 synthetic for trucks and rv's did better -- engine was quieter and ran cooler. Recently, I've been thinking of running the AMSOIL again just for increased protection for the engine.

Anyway, it's been a half year since you first posted. Any updates? Have you put in 10K miles and sent a sample of your oil in for analysis yet? Your update may help me make up my mind whether or not to run AMSOIL again.

Also, would you please clarify what you meant by your TW being super-sensitive since you installed the AWIC?

Thanks!

When I said it's super-sensitive, I mean in terms of engine response vs. temperature. When it's cooler the car seems to have more pep in it's step than it used it before the AWIC.

I didn't make the 10,000 mile mark. I got deployed on short notice a few months back and so she's gonna be sitting until I get back next year. Even though the Amsoil is supposed to be good for 1 year, the fact that it will have just been sitting with all the contaminants and moisture for so long without heat cycling or filtration makes me wary of pushing it for an extended drain interval. I can't remember the mileage, but when I get back I'll do the analysis anyways because I'm actually pretty curious about how oil holds up from sitting for extended periods.

I think I'll also do an analysis for the other 2 cars, both running dino oil (a 2010 Charger and a Saturn Ion) just for comparison.

Thanks for the clarification. And, please post the oil test results when it's done. I'm curious about that, too! Best to you in getting back safely.

Great write up on the oils. I was running Mobil 1 and recently switched over to Amsoil myself. Their headquarters are just across the bridge from me so there is a little local pride as well. I wish I was more technical like you guys are with your experiences. Unfortunately I am not so I really enjoy these write-ups!

Quick question. When I switched over, I swear my RPM's dropped between 2 and 300 at cruising speeds (70 mph). Is this possible by just changing the oil over to Amsoil? I always watch my RPM's when at different speeds so I am pretty much 100% confident in this. I would imagine it would fall into the mpg savings noticed by some.

I noticed no such change. The actual oil pressure shouldn't change unless you actually went with a lighter weight. The difference in friction shouldn't be that much between any modern oils, that's like the difference of the A/C kicking on. If you indeed saw that change, I'd attribute it to other factors and coincidence.

I had completely forgotten about my intentions on oil analysis. I still run Amsoil, but I've been using OE HD instead of Signature Series and OEM drain intervals (5000 except for when I autoX). Still using their Ea15k-20 filter, just changing it every other oil change (which was recommended by other guys who swear by Amsoil filters but also aren't enthusiastic about spending $11/at for the 15,000 mile oil).

just-rust wrote:Quick question. When I switched over, I swear my RPM's dropped between 2 and 300 at cruising speeds (70 mph). Is this possible by just changing the oil over to Amsoil? I always watch my RPM's when at different speeds so I am pretty much 100% confident in this. I would imagine it would fall into the mpg savings noticed by some.

When I ran Amsoil in my GL, I noticed a drop of rpms for any given speed. I don't recall exactly how many rpms lower, but I recall smiling as I attributed it to the Amsoil since there were no other changes done. It makes sense to me since superior lubrication means the engine doesn't have to work as hard in overcoming friction.

Hmm. Maybe I wasn't perceptive enough... but still seems weird to me that the engine would work THAT much harder with standard oil vs Am soil.

You answered another question about the filter. Good to know there is one that fits these cars. Thank you for posting that! Interesting that our motors have different results. I was giving the RPM gauge the hairy eyeball at first after I switched!

If I wasn't spending about 40 minutes a day cruising 70 mph I would have questioned it more. I have mentioned this to people and they just kind of look at me weird so I wasn't sure the response I would receive on here. Glad to see someone else who has noticed a change as well. Now I know I am not crazy! lol I hope more people chime in.

The SVX had Valvoline in it when I got it. I do remember doing a RPM comparison after but had very minimal change at cruising speeds in this car. I wonder what factors actually do lead to a difference?

That's impossible. The engine and transmission are linked mechanically and thus engine rpm for any specific gear cannot change without changing vehicle speed. Period. Unless your clutch slips or you're pressing the clutch pedal in.

Or they have automagics... like I did back when I ran the Signature stuff.

Oh lol. I always forget these cars come with autos too. My bad.

Nope. Have a 5 speed. SVX has an automagic. lol With Kimo's logic it would appear I have been hitting the pipe.

I just assumed you had an auto, because otherwise it doesn't make sense, lol.

Thanks for giving me the benefit of the doubt. lol I have a lot to learn. That is for sure!