Which is better Mobil 0W-40 or Amsoil 10W-40?

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324
Location
California
Hi, guys! This is my first message. Don't be too harsh on me. I have 96 Kia Sportage. Manual says I should use 10W-40 in most temperatures. 20W-50 has almost the same indicated temperature range, only it doesn't go too low. Right now I'm using Mobil 1 15W-50. I'm kind of disappointed with it: relatively hard cold cranking, very big fuel consumption during warm up and long warm up time (2 miles of warm up uses same amount of fuel as 10 miles at operating temperature). This car sees a lot of stop and go traffic. Used for about 12000-15000 miles/year. I really respect Mobil brand but I don't want to change oil every 5-6 months that's why I'm considering Amsoil (never used it before). Amsoil has very nice specs especially in NOACK and high shear stability. Do you think it would be safe to leave Amsoil for 1 year change intervals with above stated mileage? I probably will be using K&N oil filter. Which oil will give better protection? Fuel economy? Thanks,
 

Patman

Staff member
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21,988
Location
Oakville, Ontario
Keep in mind that when they say to use 10w40, they are based that on dino oil. If you use a good synthetic like Amsoil, you could go one step thinner and get good results. I'd go with 10w30 Amsoil for that, it's almost a 10w40 anyways.
 
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33,971
Location
Southern NJ
If you look at the recent VOA that Molekule did on Amsoil's 10w-30, there is really nothing that special about it. It also doesn't look like a long drain oil as they have reformulated it. If you want a good long drain oil, I'd try M1 0w-40 found at Autozone or Amsoil's 5w-30 HDD Series 3000. S3k is great stuff but expensive. With Amsoil, there oils use top notch components. The do buy from several suppliers and some of there oils are of higher quality, such as S3k, then there regular line. At this point, I only see there S3k being a head of anything Mobil has, other then Delvac 1. [ June 22, 2003, 08:11 AM: Message edited by: buster ]
 
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47,627
Location
Duvall WA - Pacific NW USA
Keep in mind there is nothing official about what Buster writes in regard to Amsoil "reformulating" and the oil not "look(ing)like a long drain oil" One virgin analysis and several UOA's have shown that the Phosphorous (P) varying up and down around the 1000 ppm level, but this does not mean the oil won't hold up or that the oil has been reformulated. That said either oil will serve you well. Neither have many UOA's here so there is not a ton of proof that one is superior. Your description does sound like you shouldn't go higher than a 10W at cold. 30 or 40 at temp will be fine. One thing that puzzles me: I'm thinking the viscosity and long warm up time (hence higher fuel consumption) may not be related. I would start with the thermostat and work through the diagnostics to see if the engine has issues.
 
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5,785
Location
Dixie
I think either the Amsoil 10w-40 or the 0w-40 M1 will work better than what you are currently using, which is simply too thick for this application. I like the additive chemsitry Amsoil is using in the 10w-40 and Series 3000, 5w-30. You may find it holds up a bit better than the 10w-30 formulation. Amsoil makes small formulation changes on a regular basis, about every 1-2 years based on their spec sheets. I have no reason to think they have changed suppliers. The additive chemistry did change on the 0w-30/5w-30/10w-30 oils when the SL/GF-3 specification came out last year, but that's to be expected. I honestly haven't tested the newer formulation enough to make an evaluation on it. TooSlick
 
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33,971
Location
Southern NJ
quote:
I think either the Amsoil 10w-40 or the 0w-40 M1 will work better than what you are currently using
Pablo is right, there is nothing official that they have changed formulation and one VOA doesn't mean they all are like that. I'd lean towards the Amsoil 10w-40 over the 0w-40 M1 bc I think it will be more shear stable. M1 0w-40 is a huge spread to cover and we have seen this oil thin down quite a bit in the UOA section. I'd also lean a bit towars Amsoil being more suited for longer drains (longer being over 12k +miles) then Mobil 1 due to API restrictments, although I think 0w-40 is a long drain oil meeting the 229.5 spec. [ June 22, 2003, 11:28 AM: Message edited by: buster ]
 
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