Harms nothing.
Mega 75w-90 testing thread!
- Thread starter SubieRubyRoo
- Start date
Refer to Pablo's answer then.
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- Jan 23, 2024
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- Joined
- Jan 23, 2024
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- 674
I won't need to do it for probably another year since I only did mine about 5k miles ago. But will definitely go that route. I'm going to sign up for preferred anyway and get some oil analysis kits and probably some 5w30 ss
OK PM me if you need a link for PC or here: https://www.amsoil.com/offers/pc/?zo=515729
Well, your best guide would be the testing in this thread. But always remember there is no “best” fluid, but there can be a “best for your goals”. Some of the oils have very high weld test results, which are important for manuals especially with the shock load and harsh gear engagements, but there are also 4-ball differences at lower loads, which means you can “optimize” based on how you know it’s used. Very light driving would likely choose the lowest wear result; a dedicated drag car would probably seek higher viscosity and higher weld points.
The Motul is advertised as “virtually unshearable!” and that’s pretty close. Amsoil’s results are obviously comparable and even better on some. I haven’t personally used Amsoil in Subarus but Severe Gear has always been a stellar lube even though it’s not on the J2360 QPL. Even HPL trades some wins with these two, but there are clear disadvantages to some of the choices (Gear 1 Plus with 30% KRL viscosity loss would never go in anything I own.)
I went with HPL Diff Life in mine, and as expected there’s no difference in function. I expect it will last the lifetime of my ownership without another fluid change.
I wish we could get all of the big-name gear oils done on these performance-based tests since this data is never provided by the blenders, but the lab costs involved and time to run all these tests purely for our enjoyment is a huge burden for the lab.
As @dnewton3 has pointed out a couple times, this data is great and interesting, but a nearly failsafe method of picking a great gear oil is literally as easy as pulling up the J2360 QPL and throwing a dart at that list. If you read the qualification tests required to make the list, they’re very in-depth on results-based evaluations; any gear oil on that list is going to perform very well, but some will still be better than others when viewed with results like in this thread. J2360 gives us a “performance floor” to say these minimums were met by all gear oils on the list regardless of other testing that may show “subpar” results in our opinions.
Side note- HPL will recommend the 75w90 Diff Life for Subaru diffs. You won’t need the Cold Climate version, but if you want a PAO-based fluid you can always order it up anyways.
Please tell me where I can buy 6-7 quarts of Amsoil SVG 75W/90 in the easy-squeezy packs, for only $15! It's $22 on their website. (Or did I misunderstand your statement?)
OTOH, I can order that quantity of Valvoline 75W/90 in the "flex fill" package from their website at $15.29 (with free shipping).
For a 4Runner that basically never experiences subfreezing temperatures (I live in Las Vegas), doesn't tow, and gets fluid changes every 30K miles, seems like the Valvoline is adequate for both diffs and the transfer case? I do a certain amount of four-wheeling, does that fact alone tip the balance toward Amsoil? I put in the SVG at the first change, but I wonder if it's overkill for my use case.
Preferred customer price is $17.29. Is it worth it? Depends more on how long you will run it. $2 qt more, not a huge difference.
It's not free to become a "preferred customer." Not really cost-effective for someone who only buys a few quarts of gear oil every ~1.5 years.
As stated in my post, I change the fluids every 30K.
I personally rebate the PC fee if you sign up with me, but no pressure use what you want.
30K no problem for SVG, maybe the limit for Valvoline.
Sorry about the delay replying, life intervened. Assuming free shipping for the 7 quarts of oil, then this seems to be a good deal. Where do I sign up?
How does pennzoil synthetic 75w90 stack up?
@SubieRubyRoo, if you ever get bored and want to do another one of these comparisons again, maybe do one comparing one brand, different grades: like Amsoil SevereGear 75w85, vs their 75w90 vs their 75w110, vs their 75-140. Or do all HPL. We can use their PDS’s to get viscosity differences, but I’m curious what the 4-ball wear and weld tests might reveal across their various grades (and assuming equivalent quality), as well as KRL, and maybe the PDSM. Of course, it still might be useful to throw in an OEM 75w85 (like Motorcraft) since those are getting so prevalent. I’m curious if there is any magic employed to get the 75w85’s to perform better than the more traditional 75w90’s. It might also be useful to have a viscosity reading at 32f (0C), which might get some “thickies” to reconsider, assuming the 75w-85’s have a clear advantage at that temp.
ACDelco 75w90 came in 3rd on the 4 ball wear test 
and not bad density ranking for a high VI, low viscosity oil! Plugs have always come out clean on the ATS with almost 100k miles on it now. Going to change it for the 4th time in the spring, so the diff has had a lot of fresh fluid with 30-35k mile intervals.
I've only used ACDelco on the ATS since new... but it's pricey, but now that it's out of warranty I'm looking at the Valvoline and LiquiMoly 75w90 GL5 on my shelf at less than half the cost.
I like to check/replace the breather valve on the diff when changing the fluid too... so far it's clean as a whistle at 100k miles.
and not bad density ranking for a high VI, low viscosity oil! Plugs have always come out clean on the ATS with almost 100k miles on it now. Going to change it for the 4th time in the spring, so the diff has had a lot of fresh fluid with 30-35k mile intervals.I've only used ACDelco on the ATS since new... but it's pricey, but now that it's out of warranty I'm looking at the Valvoline and LiquiMoly 75w90 GL5 on my shelf at less than half the cost.
I like to check/replace the breather valve on the diff when changing the fluid too... so far it's clean as a whistle at 100k miles.
@HPL Plant Manager could you please provide the lab test results for the different viscosities of Gear Life so we can expand our knowledge base? Thanks!