So....this is basically the question. I was able to find many quarts of Quaker State Full Synthetic oil in 10W-40 weight. My thoughtis to mix3 quarts of 10-40 and1 quart of 5-20 (all synthetic)for an equivelent of about 7W-35.

Likely going to run this weight only in the summer -- in winter here in the northeast (Massachusetts), I'd run 2 qts. 10-40 and 2 qts. 5-20, for about a 7W-30 winter weight.

So....is a 35 weight in summer too heavy?

 

first, we dont know what you're driving.

second, the heaviest oil called for by mitsu is 10w30. most take 5w30, and everything since 04 takes 5w20.

so yes, what you're planning on using it probably too thick.

 

Mixing different weights doesn't mean you what you get is an average.

Stick to what Mitsubishi recommends as it will be applicable year-round. If you're worried about engine protection with 5w20, there are synthetic applications available, such as Amsoil XL 5w20 (XLM), made for 7,500 mile oil changes

 

not to mention, are you seriously considering putting quaker state in your car...
youll be lucky if it runs at all, after you abuse it with that ****tydinosaur excriment they call oil

 

Well.....to answer the questions, I'm driving an 03 Outlander, and am simply using the QS synthetic because I got 18 quarts of it for $1 per quart. Likely because it is 10W-40. So, my plan is to mix the 10-40 with the 5-20 to thin it down. 2 quarts of each....

 

though i could be mistaken, i'm under the impression that as viscosity is basically on a molecular level, your mixing two multi-grade lubricants is not going to do what you've mentioned, unlike the more volatile carbon chains in different octane-level fuels which can yield a higher octane number when mixed in certain measures.
really, why do you want to 'thin' your oil? if you have a multi-grade, the oil will flow through engine orifices like a thin 10 weight, and resist thermal breakdown like a thicker straight 40 weight. i checked my outlander manual for its oil recommendations, and as long as the ambient temp doesn't remain for long periods over 100 degrees, all-weather 5 or 10(w) - 30 is sufficient, but as 10w-40 flows as easily as 10w-30, what are you worried about? the internal engine drag and oil pressure increases that might occur with a heavier wight oil are minimal in a street car, and you only have to worry about shear if you're driving straight through death valley at high rev's/speed.
if you're really that concerned about thinning your oil, bite the oil bullet and just change it using 5 or 10w - 30 full synthetic. depending how many miles are on it, you might want to consider using a motor flush - i've
used it from new on my '93 expo at least every other oil change, which was faithfully done every 3-4,000 miles or 3-4 times per year, and after 250,000 miles and still going strong with no oil burning, i'd say the stuff works....i let my dealer do one of those internal steam cleanings 100,000 miles ago for the purpose of removing sludge; they told me very little if any was removed....better yet, see if your dealer or repairer offers that internal flush and have it done, and then use the liquid flush yourself periodically therafter - and stay with the full synthetic!

 

Hi,

I don't like the idea of mixing 2 different oils either, for the same reason expositor mentions. Also the European manual warns to never mix oils. Just stick with a good synth I'd say.
I let my Mitsu dealer do the oil changes, he only has one kind of synthetic right now and it's Agip 5w40. Seems to run fine, and my fuel efficiency is very good too, but I'd prefer to try a thinner oil like a 5w30..
I've looked around and the products that interest me most are Castrol Formula SLX LongTEC 0W30, or Castrol Syntec 5W30... Mobil 1 5w30 or Pennzoil Platinum 5w30. A lower viscosity should give a tiny bit better performance and should be more fuel efficient
By the way expositor; I'm curious what oil brand you've always been using in your strong '93 expo, it certainly was a decent oil! but you've also taken good care of your car I read

 

hi light,

to begin, i second the 'diamonds forever,' and ANY diamond is worth appreciating!!! i think like that 5w-40 synthetic your dealer is using, though that name is new to me. anyway, my first oil change in the outlander was at about 1200 miles and i used 10w-30 mobil 1, and then at about 5,000 or so, after a flush, wal-mart 10w-30 full synthetic as it's quite a bit cheaper at $13.82 for a 5-qt jug. in the expo i used whatever oil was on sale, though i often used the supermarket brand 10w-40 in winter, and 20w-50 every summer. those off-name brands are all mfg'd by a big-name oil company; you just need to make sure that the appropriate warranty and api usage labels are there. i've been tempted to change to a 10w-40 full synthetic, but as the 30 is ok per the manual, i think i'll just stick to that for now as 40 is probably unnecessary here in new joisey. i'll speak with the my dealer's service dept about using the 40 just to be sure when i take it in for a routine service, sans the oil change of course. being of an age older than most in the forum, back 'in the day' as they now say, with the higher rev's and lower differential ratios of 4-cyl drivelines, especially before widespread use of five and six speed manual overdrive transmissions, using all-weather 40 and 50 oils was common, and old habits die hard....

 

oops...'i think i like that...oil....' posting haste does indeed make....

 

hmmm....try 20-50 next time.