10w-30 in 100+ degree weather?? Charts says NO!

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Dec 13, 2002
I have a 2000 Kia Sportage 4x4. The oil was recently changed with Mobil 1 10w-30 oil. Reading the truck manual today, I noticed a chart that lets me pick the weight of oil depending on ambient temp. The chart says 10w-30 is good up to 85 F. Should I take this chart as the gospel? Are these charts really for my specific engine?

I will be in 100+ degree weather soon (highway driving, up mountains, down mountains...idleling at stoplights, etc.)

It's no big deal for me to change the oil if I have to (c'mon, we've got it down to 5 minutes, right?). I'm leaning toward change (better safe than sorry...pretty good moto). Should I move to a 10w-40, 15w-40, etc??

Your expertise is appreciated!!

[ May 24, 2003, 01:57 AM: Message edited by: turbochem ]
I wouldn't think it would be a biggie. I have been running M1 0W30 in my Firebird for two years now, no problems. I live in N. Ga., plenty of hot summer days. I also beat the heck out of my car, no abnormal oil consumption,,good oil pressure,,, yada yada yada.

On my last change I switch to 0W40 not because I thought the 0W30 wasn't working well but because I figure the engine has loosened up bit and I've been seeing some good reports on the oil.
If it was my vehicle, with Mobil 1 10w30 in the crankcase, I'd leave it in there & not worry one bit about using it in hot weather, no matter what the owner's manual said. JMO.
Most are engine specific. I have two cars of the same year and a few with years apart and it is amazing how the charts differ. Most say 5W-10W30 to over 100 degrees some give the option of 15W40 over 32 degree as a low etc. One has 5W to only 70 degerees or so. However, oils and formulas change, owner's manuals do not. My 92, well I could not find an SG rated oil if I wished to but 10W30 is still around

Engine specific. If it permits a higher weight oil in the manaul I would use that year round unless the temp really falls in the winter.
turbochem - that seems like an old style chart.

Lemme ask this: does the bar stop with a straight line, or an arrow???? (on the 10W-30)

The fact that M1 (or any modern 10W-30) can't handle 85° F seems ludicrous - does the engine have some huge tolerances?

Originally posted by turbochem:
It's not an arrow, just a bar that goes from -10 F to ~85 F.

My Dodge Avenger has a similar chart:
5W-30 = -40F to 100F
10W-30 = 32F to......(no high-end)

So I'm only supposed to use 5W-30 upto 100F. I don't think I've experienced temperatures higher than 100F except once while driving through Arizona.

Kia's recommendation probably has less to do with the oil than oil capacity and engine RPM.

I'll bet the oil capacity is less than 4qts and the engine is taching it up pretty good at freeway speeds, >3000rpm@70mph.
This should come as no surprise to the regulars of this board. Here is a manufacturer that has spec'd out different oil grades based on temperature rather than CAFE.

As I said before, heat is the #1 enemy because you will not get sludge and varnish from cold. But what does this mean? Of course an ANY 10-30 can withstand 85F. This isn't the engine temp. when the ambient temp is 85...especially when you shut the engine off. What do you think the engine temp. is when you first shut the engine off in 100F weather? You guessed it...it skyrockets...this doesn't happen in the winter.

And although the chart is primarily based on conventional oil...the grade should be maintained when using synthetic because grade is more important than type of oil. I'd suggest you stick with the recommended grade...

Originally posted by Dr. T:
As I said before, heat is the #1 enemy because you will not get sludge and varnish from cold.

Are you kidding? Take an engine running conventional oil that never gets warmed up enough to burn off the moisture and acids that form in a cold engine, and you've got a sludge monster.

Lemme ask this: does the bar stop with a straight line, or an arrow???? (on the 10W-30)

It's not an arrow, just a bar that goes from -10 F to ~85 F. However, the 10w-40, 10w-50 lines go all the way to 140 F (basically off the chart), along with 20w-40 and 20w-50.

It actually has bars for a plain 40 and 30 weight along with something called a 20w-20!!!! It shows that a 5w-20 can't be used above 0 degrees F and 5w-30 can't be used above 32 degrees F!!!! LOL....Not sure what to make of this chart.....
There are 10 possible weights to choose from.....

Quote from the manual "[H]igher viscosity engine oils are required for satisfactory lubrication in hot weather. Using oils of any viscocity other than those recommended could result in engine damage." How's that for a dire warning??

Troy, thanks for your concern for my Kia purchase.......I know the "reputation" and perception.....It's a great car...had no problems.....

[ May 24, 2003, 12:33 PM: Message edited by: turbochem ]
Keep in mind that those charts are basing it on your average 10w30 dino oil, and a good 10w30 synthetic will easily handle the heat better.

I'll bet the oil capacity is less than 4qts and the engine is taching it up pretty good at freeway speeds, >3000rpm@70mph.

The capacity is 4.4 quarts (the engine is based based on the 2.0L DOHC Mazda FE3 engine...BTW...)...The engine likes to rev more than any other car I've owned. You're pretty much on the money about RPM's at 70.

Just bought some Mobil 1 15w-50 to be safe.......Thanks....
Hyundai is Kia's parent company, now. I have a 2003 Hyundai Sonata with the 2.7 liter V6, and the owner's manual lists 90 degrees F. as the upper limit for using 10W-30. I asked the dealer's service manager for clarification. His answer was that they use 10W-30 Quaker State in customers' cars year round in inland southern California with Hyundai USA's blessing despite what the Korean printed manual says. We see two or three weeks in July and August in excess of 100 degrees, and last week had three days nearly into the 100s. More of the same expected by the middle of next week if the local weather jerks are right. (I picked the wrong occupation. Other than politics, what other profession pays so well for being so wrong than reading a prepared script of the weather forecast on local TV stations?...) My '91 Sonata's old Mitsubishi-based V6 owner's manual said the same thing - apparently Hyundai Korea is a bit slow to upgrade their recommendations. I put 90,000+ miles on it in five years before I traded it in disgust for a 96 Accord. (Couldn't keep juice in the A/C and no one could figure out why.) It never leaked or used 10W-30 oil in all that time, though, and the engine was still strong and sounded good - cold or hot. My 2003 Hyundai Sonata manual still recommends use of SG and SH oils, too, identical to the 1991 manual. The viscosity spread of a 10W-30 oil is 20 pts, but 30 pts and 40 pts respectively for a 10W-40 or 10W-50 oil in hot weather operation with conventional dino oils (Group-II or Group-II+). If you feel you must take extra precaution in extreme heat, I'd suggest 15W-40 heavy duty fleet oil, if conventional, or going to full synthetic with its inherently higher viscosity index base oil. I plan to continue with 10W-30 in my car, though.

[ May 25, 2003, 03:35 AM: Message edited by: Ray H ]

We see two or three weeks in July and August in excess of 100 degrees, and last week had three days nearly into the 100s.

LOL...reminds me of my childhood in El Centro.....we'd practically combust during the summer........

I'm going with 15w-50 Mobil 1.......

Hoping my tires don't melt in the Arizona sun.......

[ May 25, 2003, 01:30 PM: Message edited by: turbochem ]
It is best to follow the API temp/vis chart they have been kind enough to supply you with. With that said with synthetic in it if you do mostly short trips you will be fine. If you plan on driveing 95MPH in 100 degree heat I would prefere something thicker like 15W50, 15W40...... Your engine is not going to self destruct or anything like that. The chart is based on dino oils. Dino 10W30 is not shear stable at prolonged highwas speeds or high temps and shear loading. The VI's start to shear and break down. I have never used 10W30 synthetic or otherwise in anything that see's alot of hwy driveing or high temps. The API temp/vis chart is the best guide for oil recomendations!!!!
I'm going to have to go out in an hour or two and look at my '01 Elantra's manual. I thought it allowed 10W30 to 100+. I've certainly been using 10W30 SuperTech steadily except winter in this car. I did take it in to the dealer a couple of months ago and they use 5W30 Castrol dino year around, probably because they also sell Nissans, VW's Suzukis and Isuzus. I wouldn't feel comfortable with 5W30 in summer with this engine. On the other hand they do allow 10W40, something I found strange when I read it. I would think 10W40 would sheer back rather quickly, I didn't know this was a viable oil in most new cars. The Sportage is probably a far different and cruder engine than that in my Elantra, however.
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