Can I use 10w40 in my vehicle?

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Aug 13, 2011
Picayune, MS
My vehicle calls for 5w30, and 10w30 in the right conditions (i.e. summer driving). I found some cheap 10w40 that I posted about from Valvoline and I'm wondering if it would be fine in my vehicle. It's the Hyundai in my sig. Would I need to buy more oil to mix in with it so it takes down the viscosity more? If so I may return it because I won't have much use for it. Can I use full 10w40 in my SUV? Thanks!
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Of course you can use it. But it may lower your gas mileage by 1-2%, will vary with car, and this loss may only be temporary. My car also calls for 5W30 or 10W30. I had some 10W40 Valvoline that I used in an oil change. Car takes 4.5 quarts; I mixed 1 qt 10W40 with 3.5 qts 5W30. I did not measure mgp, but rpm dropped immediataly at idle by about 100 rpm. This was only temporary in my car. After about 2 weeks, the rpm's were back to normal. ________________________________________ 1999 OLDS GLS 3.4L
Being in South Dakota I would use it as top off oil in the Summers. It is crazy cold there from what I understand. During colder months I would stick with your synthetic 5w30 and what not with the really low pour points. I'm currently using a 40 weight in my 2002 Ford Taurus with its 3.0 SOHC V6 and 176,000 miles. However, It has a small leak that the 40 weight really slows down, and it only gets down to the 40's at night here, then back up into the 70's and 80's during the day. Can you use it? Sure, but I'd be careful with your winters.
You could use it as a summer fill. But not in winter, run a 5w30 or 0w30. not sure what part of the state your in, but it gets cold pretty much everywhere lol
Summers can get up to an average of 80-100 degrees, spring usually floats around 68-74. This would definitely be a summer oil. I have to take it back anyway because I found out they charged me $3.99/qt when it was marked for $1.99/qt. So I either may return it or just have them give me my money back fully. Thanks for the responses!
here's a thought -- your vehicle calls for 5w-30, so buy 5w-30 and use it. i don't understand why there are so many threads devoted to this topic -- can i use a (thicker/much thicker)oil in my car that calls for a 5w-30, or a 20w oil? 10w-40 won't hurt anything, but using that logic, go with a 20w-50, or mabye a 10w-60.not being sarcastic -- just go with the spec'd grade.
Running a grade heavier than spec' oil because it was cheap is usually false economy due to the reduced fuel mileage (whether you can measure it or not), unless the intent is to use it for blending purposes with a lighter than spec' oil.
In ND I'd defiantly use it in the late spring, summer and early fall, then my right foot weighs about 40Lbs, gas mileage isn't a concern...
I have to wonder about the dangers of using a 10W30 or 10W40 oil in wintertime.... Back in the 'day' (1950s and 1960s) these 10W oils were the WINTER OILS!....and we worried about the "danger" of using these "W" (Water weight :)) oils in the SUMMERTIME!
I swear that I have read on either this site or another that the multi weight oils 10/40 for example, are suppose to perform as a 10 wt. oil when cold, but retain the viscosity of a 40 wt. when hot. Is that right? so wouldn't warm weather use of a 10/40 be ok.
You don't have swear, I believe you. Technology marches on and 10W-XX oils are no longer recommended for winter use. They are much heavier on start-up at all temp's than 5W-XX and 0W-XX oils. A 40wt oil is simply heavier than necessary for your application.
Absolutely you can! Won`t hurt a thing. If you lived in Australia,here`s what Shell says: Premium HELIX ULTRA 5W-40 Standard HELIX HX7 K 15W-50
I'd return it for a refund. I've used 10W-40 in 5W-30 spec engines with no problems in warmer weather. If there was an increase in fuel consumption, I never saw it, and I track each tank of fuel in all of my cars and have for thirty years or so. Thirty years ago, we used 10W-40 all of the time in everything. 10W-30 seemed too thin, and in 1980 it may have been, given the quality of the oils then available. The only reason I'd use a 10W-40 in your Hyudai would be that it was dirt cheap. It is not optimal, but would be fine for a summer run. $1.99/qt is not dirt cheap, so I'd return it.
The Professor recommends to use a good conventional oil for your application. The Professor personally recommends Quaker State High Mileage 5W-30.
Not sure about this professor guy but thanks for the replies everyone. I returned it tonight, see my thread on my mobil I ended up buying.
I think the real problem of using 10W-40 oil is that it doesn't have the 'starburst' symbal on the container, saying 'for gasoline engines'. This is generally what car manufacturers recommend and some insist on, with current production vehicles. It's not as stupid as it sounds, but there is a reason for putting that symbal on the container.
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