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5W30 vs 10W30


Last Edited: July 28, 2007, 5:32 pm

I've been doing a lot of driving over the past few weeks, so I decided to get an oil change today and purchase new windshield wipers.  Since the manager of the local Tire Kingdom was very nice to me last time I was there, I decided to go there instead of the dealership.  Actually, the Toyota dealership is also very helpful, but they're more expensive and I don't need my tires rotated or any of the extras this time that might justify charging $34.95 plus shop fees & tax for an oil change. 

When I got home I noticed Tire Kingdom used 6 quarts of 10W30 and I know the dealer uses 5W30.  I realize that the 5W30 is thinner and is recommended for colder climates and that 10W30 is pretty standard.  But I've also read online that using the high viscosity oil could result in "sludge" building in the engine.  I've been on sites like Cars.com and others have asked the same question about which oil to use.  Most answers said to use 10W30 in a mild climate. 

I've learned the hard way that, when in doubt, read the Owner's Manual which specifically says to use 5W30 in all climates and says that 10W30 will result in poorer gas mileage.  It also says that if it's necessary to use 10W30 because 5W30 is not available, to change to 5W30 next time the oil is changed.  Mobil1 is what the dealer used.

This really concerns me.  Isn't Mobil1 synthetic?  Will this change to the other oil void the warrantee?  Would you go back to Tire Kingdom?  I guess using it only this once shouldn't have any damaging effects, but I'm wondering if they used the 10W30 because it was cheaper.  The receipt says "bulk oil" and I'm not sure what that means exactly, except they buy an awful lot of it! 

Okay - just read more information on the recommended oil (which is still 5W30) but there are several people who say that in very hot weather 10W30 is actually better because it won't break down and provides better lubrication.  Except for Death Valley and Phoenix, I doubt if there could be many places hotter than Southwest Florida!



Entry #73


JAP69Comment by JAP69 - July 28, 2007, 5:56 pm
This really concerns me. Isn't Mobil1 synthetic? Will this change to the other oil void the warrantee? Would you go back to Tire Kingdom? I guess using it only this once shouldn't have any damaging effects, but I'm wondering if they used the 10W30 because it was cheaper. The receipt says "bulk oil" and I'm not sure what that means exactly, except they buy an awful lot of it!

Yes mobil 1 is more expensive about 6 or 7 dollars a guart.
bulk oil I think would mean is that they buy it in 50 gallon barrels.
If you are within your manuals recomendations I would think you are good to go.
justxploringComment by justxploring - July 28, 2007, 6:22 pm
Thanks, JAP69, but that is my point. According to the Owners Manual, 10W30 is not recommended and this is what Tire Kingdom used. So maybe the more expensive oil change at the dealer is worth it if they use a better product. At least I won't have to worry about warranty problems later on.
Comment by pacattack05 - July 28, 2007, 6:27 pm
I use WD40, it works just fine.
four4meComment by four4me - July 28, 2007, 6:31 pm
10w30 is fine for the summer time
justxploringComment by justxploring - July 28, 2007, 6:32 pm
Interesting - lots of discussions about this topic online. Some people disagree with the manual and say to use 10W30 in the hot summer months. Another person said that the synthetics have additives that might be harmful to an engine, so not to use a synthetic. One person seemed to have the definitive response to someone asking the same question. (1) Use the dealer. (2) Use the dealer (3) use the dealer and (4) guess what I was going to suggest?
justxploringComment by justxploring - July 28, 2007, 6:47 pm
Thanks, four4me. Makes me feel a little better. You can see I was typing when you posted. I guess driving 3,000 miles with the 10W30 won't hurt the engine. In the past, any time I've had a problem with a car, if I used my own mechanic or had service performed at a shop other than the dealership, they always blamed the problem it on me. When I used the dealership all the time, they were much more forgiving.

WD40? Pac, at least you didn't suggest KY-Jelly.
justxploringComment by justxploring - July 28, 2007, 7:02 pm
Hi....me again. It's nice to know I'm not the only one who has asked this question. Guess the bottom line is M-O-N-E-Y !!   They obviously want to use the oil they buy in quantity and put in most engines. However, I really think they should have used what was indicated on the sticker on my windshield from the last oil change which said 5W30, or at least questioned me. I had no idea that in tiny print the coupon specified the "bulk" oil. A few extra dollars wouldn't have bothered me. After all, I just put the most expensive windshield wipers I've ever seen on my car. This is what Car Talk says
Dear Tom and Ray:

My husband and I disagree about what grade of oil to use in his '99 Explorer. He refuses to take his car anywhere other than the Ford dealer because he gets mad when he sees others use 10W30, when the owner's manual calls for 5W30. It seems that everybody uses 10W30 at the non-Ford dealerships. I guess I should also mention that we live in Texas and don't get the cold winters that people get up North. But my husband claims that there HAS to be a reason other than temperature why Ford wants 5W30 in its engines. Why do they recommend 5W30? Give me a good answer, or I might have to trade in my husband before the lease is up! -- Linda

Ray: Well, we should first tell you what the multi-viscosity numbers mean. 10W30 means that the oil acts like a thinner, 10-weight oil when it's cold and like a thicker, 30-weight oil when it's hot.

Tom: So a 5W30 oil would be the same as a 10W30 once the engine is hot, but it would be thinner when the engine is cold (when it hasn't run for several hours). And that's why Ford, and most manufacturers, now recommend it.

Ray: A thinner oil flows and spreads more easily when you first start the car. And the faster it spreads, the more quickly it lubricates important moving parts. Presumably, that makes the engine last longer, because less friction damage is done during those first few seconds after starting.

Tom: How much difference does it actually make? We have no idea. Probably not a whole lot. It certainly makes less of a difference in Texas, where the outside temperature stays higher and the oil never gets quite as viscous.

Ray: So I'm sure it would not be a disaster if you used 10W30, but given a choice, I'd go with Ford's recommendation and use the 5W30.

Tom: And the reason a lot of shops use 10W30 is because it's the closest thing to a "one size fits all" oil.

Ray: Plus, mechanics love what it does to their hair.

justxploringComment by justxploring - July 28, 2007, 8:42 pm
Oops! Dealer did not use Mobil 1. Used Mobil SAE 5W30. I thought the S stood for synthetic but it's just an acronym for Society of Automotive Engineers. No biggy! :-)

jarasanComment by jarasan - July 28, 2007, 8:47 pm
The key is changing your oil regularly, the engine oil becomes contaminated that is why it needs to be changed regularly because the contaminants affect the oil's ability to lubricate properly. I have a Toyota 4runner it has 177K miles on it, it has had regular oil/filter changes every 3k to 5k miles since I've owned it, and it has had either 5W30 and 10W30 in it the whole time no problems. You have to remember that with every successive oil change the old oil is never 100% removed, there is always a little of the prevoius oil left in the engine no matter what, so you actually have remnants from the original oil that the engine came with when it was off the assembly line. I love my Toyota, it is my second, the first made it to 155K and people were fighting over it to buy it when I sold it to get the current one. I think my last one a 1984 4X4 is in Paraguay or Nicaragua.
Comment by pacattack05 - July 28, 2007, 10:19 pm
WD40? Pac, at least you didn't suggest KY-Jelly.

Should I have?...lol
Atleast we know where it's made...lol....In Kentucky...lol
Comment by pacattack05 - July 28, 2007, 10:27 pm
You are a woman with variant views. I respect this.
Comment by pacattack05 - July 28, 2007, 10:35 pm
I change my oil all the time...lol...
Maybe too much....lol
truecriticComment by truecritic - July 29, 2007, 12:49 am
SAE is important. Look at some quarts of oil. You will see SAE specs normally on the top of the can. Most oils have the same specs - but some don't.   Each combination of letters on top of the can represent a certain spec.   Many people aren't too fussy about 5w or 10w but they do insist on certain brands of oil. In reality, if they compared the SAE specs, the brand itself wouldn't be too important.   They can use any brand(s) that had the same specs.
justxploringComment by justxploring - July 29, 2007, 5:13 am
Thanks True Critic and everyone for your comments. After I posted my original comment, I discovered that this is one of the most commonly asked questions about engine oil. Living in a very hot climate, I realize that 10W30 will be okay and won't ever be too cold, although in a few months I should switch back to 5W30.

Jarasan, I agree that maintenance is important. My dealer said every 5,000 miles is fine. After this last oil change, however, I will probably go back to Tire Kingdom in 3,000 or less. I also have a Gift Cert for an oil change with "bulk oil" so I'll ask if it costs more for 5W30 or a brand name. I know they sell Pennzoil at Tire Kingdom. That said, True Critic makes a valid point. I think it might be like buying generic Tylenol or Advil. Many people don't notice a difference and say since they all have to meet FDA regulations and contain the same ingredients/strengths, you're wasting money with name brands, but I often notice a difference.

Rick GComment by Rick G - July 29, 2007, 11:13 am
My vote is 5W30 for engines under 75K miles and 10W30 for those older. It's not a good idea to use synthetic oil unless your engine has started and stayed with it during its lifetime. Don't worry about the "bulk oil" label. Ask what brand they use and if you've seen it on the side of a NASCAR racer you know its OK....   ;)
justxploringComment by justxploring - July 29, 2007, 1:03 pm
Thanks, Rick. Well, I have learned so much in 24 hours!! I guess 2 or 3 months won't make that much of a difference. I know now to tell the shop what to use, or maybe just go to the dealer. I don't want to sound cheap, but when you have a Gift Certificate it's hard to throw it away and it said "for oil change" not for "service." If anyone is interested, here is some info from an informative site:

Climate Considerations
Owner's manuals and service manuals will specify the acceptable oil to use at various temperatures. In warm climates, 10W30 is usually an acceptable alternative to the preferred 5W30 and may be used without measurable adverse effects. In the olden days, before multi-weight oils, it was common to have a winter oil and a summer oil. This is no longer necessary, but if you normally use 10W30 because you live in a warm climate then be sure to switch to 5W30 if you plan on using the vehicle in very cold weather.

5W30 versus 10W30
Virtually all new passenger vehicles sold in the U.S. use either 5W30 or 10W30 oil. The difference between the two is that the 5W30 flows better when cold, so if you live in a cold climate or operate your vehicle in a cold climate during the winter months, you should use 5W30 if it is the preferred oil for your vehicle. If you live in a sub-tropical climate and don't operate your vehicle in cold climates, then 10W30 is acceptable as long as the manufacturer specifies that it is permissible to use it.

Is there a disadvantage to using an oil that flows better when cold, i.e. 5W30 versus 10W30?
Sometimes, but usually not. The crux of the issue is this: the bigger the difference between the cold oil viscosity and the hot oil viscosity, the more the volume of viscosity modifiers and the less the volume of base stock. If you are good about following the manufacturer's recommended oil change interval then stick with the 5W30 if that is the preferred oil for your vehicle, even if 10W30 is acceptable in warmer climates. Older cars may specify 10W30 only. This is because they need a little more viscosity when cold to keep a protective film on the cylinder walls. There have been instances where the larger amount of viscosity modifiers that are present in 5W30 have broken down due to excessive heat and have left carbon deposits on the valves, but this is extremely rare. The proper fix would be to reduce the excessive heat, but the workaround was to use an oil with less viscosity modifiers.
JAP69Comment by JAP69 - July 29, 2007, 3:54 pm
I was thinking about the old days today about oil.
I can remember the 10 and 30 weights changing from summer to winter.
When I use to have a car that started to burn oil I use to put 40 weight in it. Along with ring seal additives.
justxploringComment by justxploring - July 29, 2007, 7:33 pm
I remember 10W40 was pretty common, although I was never really mechanical. I just recall seeing it on my receipts.   

Well, I had another short panic attack. But I figured it out. The warning light for maintenance wash flashing and wouldn't go off. I think I was able to reset it...pretty simple actually. I had my last oil change at the dealership at about 23K miles and I have 27, 700 and the manual says that's when it will begin to flash. So I guess it was just a coincidence that it happened right after I had the service performed.

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