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Motor oil selection

I live in Columbia,SC. I own a 2001 Toyota RAV4 2L, a 2003 Dodge Caravan 3.8L, and a 2007 Dodge Ram 1500 3.7L. The 2001 and 2003 require 5W-30 oil, and the 2007 requires 5W-20 oil. Can I safely use 5W-30 in the 2007?

Safely? Sure. Recommended? Not really. This topic has been discussed many times before.

Honestly, I would, but that does not mean it is actually a good idea.

Modern cars use oil as a coolant. Oil that is too viscous does not cool as effectively as ‘thinner’ oil. If the 2007 were still under warranty, you would definitely not use it because it would void your warranty.

Probably. You live in a moderate climate and would not have the same lubrication issues that someone in MN would driving the same Ram truck. If they can use 5W20 in winter, you cane likely use 5W30 i winter. And the manufacturers use oil viscosity as a way to improve gas mileage. Using slightly thinner oil means that moving lubricated parts is slightly easier, which increases gas mileage. You won’t notice much difference, but it allows them to meet their CAFE requirements more easily.

This seems to be a very plain spoken analysis of the situation.

Key sentence:

“The common 10W/30 has become a 5W/30, and some manufacturers even recommend 5W/20 oil. On the other hand, we can’t see (in oil analysis) where it hurts anything to run heavier 10W/30s or even 10W/40s in modern automotive engines.”

Living in the climate you live in I wouldn’t hesitate to use the 5w30. The recommended oil for my cars are 5w20 and 5w30. I live in a colder climate than you do yet I use 10w40 year round in all my vehicles and haven’t had any problems. One of them has over 500K miles, 2 of them are near 200K miles, and two at between 120-130K miles. The only one that uses a significant amount of oil is the one with 500K miles which uses a quart every 800-1K miles, I suspect the rings are about worn out in it. None of the others use more than a quart every 5K miles.

When I bouht my 2007 Toyota, the manual called for 5W30. Two years later a Toyota bulletin comes out and 5W20 is all of a sudden recommended.!!! So draw your own conclusions. The dealers are pushing 5W20 since all new Toyotas call for 5W20, msotly to meet CAFE fuel economy standards. The dealers want to minimize heir nventory of course.

A few years ago I had a company Ford Explorer. The manual called for 5W20 in one engine and 5W30 in the other optional engine. The 5W30 oil engine probavly had still the old clearances and poor seals and would gulp oil at high speed and heavy loads. As OK says, once an engine is warmed up, 30 weight is usually better. In tropical countries those cars still use 20W50 in many cases. Just visit Southern Mexico and stop as a gas station and read the oil labels.

You can, but do you really want to begin using fluids other than those recommended in the owner’s manuals? I wouldn’t.

The difference between 5W20 and 5W30 is the amount of “viscosity modifiers” in the oil. Viscosity modifiesr are microscoping polymer coils that expand with rises in temperature, affecting the ability of the oil to flow and keeping it’s resistance to flow (called “viscosity”) greater at higher temps. This enables better ability of the oil to stay pressurized in the bearing spaces in the lubrication system, allowing it to better maintain a pressurized barrier between the crank and rod surfaces and their respective bearings when hot. However, there are no free lunches. The modifiers don’t lubricate or remove heat as well as the oil itself. That’s whay it’s recommended never to go beyond 30 in the difference between the base weight and the elevated temperature “weight”. 10W40 is okay (if allowed by the owner’s manual), but you’ll never see 10W50.

In short, you should use what the owner’s manual recommends.

Docnick, you are absolutely correct about the heavy oils in Mexico. It is very hard to find 5W30 or 10W30 anywhere, including AutoZone.

I was trying to find a quart of 5W30 or 10W30 Quaker State, (I am in my dino oil experiment project) since my Sienna uses a quart between oil changes. I went into a local store and they had it, but not QS.

The knucklehead told me not to use 5W30, because it wouldn’t hold up. Everyone here on this forum knows better, the temperatures here are moderate year round. But, this nonsense gets passed down and everyone believes it. So, it is like a cultural norm here that you gotta’ use oil designed for the diesel compressors used in the quarries on a good car.

I must wonder if this doesn’t cause increased motor wear.

Your 2007 is likely out of warranty, yes. The 5w20 offers a tiny bit of MPG increase.

I have a vehicle(2007 Acura MDX) that requires 5w20. Out of warranty it gets 5w30 at my mechanic. No difference in MPG.

I think you should follow your owner’s manual. I tend to think there is a reason for everything a manufacturer puts on paper. You do not want to have some sensor to misinterpret oil viscosity as an engine problem.

Is there a sensor that can misinterpret oil viscosity, Stig? Does the ECM have any access to monitor engine oil level, pressure, etc.?

@tsm 10W40 is okay (if allowed by the owner’s manual), but you’ll never see 10W50.

10W-50 no…but 5w-50 -YES. But only in a full synthetic oil.

While I too would like to know of such a sensor, I do agree with Stig’s comment. The manufacturer does know best.

Sorry, Rod. I know what you were really saying.

Like most manufacturers specification, oil viscosity is 'nominal.; The manufacturers seem to prefer to take the simplest and least controversial option of recommending the oil that would be most often correct. Certainly, the improvements in the mechanical tolerances in engines has lowered the viscosity that is ideally suited to newer engines but there is likely still some benefit from considering the ambient temperature to determine the ideal oil for your engine. But when in doubt, use the grade specified on the cap or owner’s manual, of course.Presently I service 4 vehicles regularly. 2 are old trucks that I would use 10-40 in but then 2 have recommendations of 5-30 so I split the difference and use 10-30 in all of them and feel somewhat confident that there won’t be any problem from any of the engines. Unlike user names and PIN numbers, oil viscosity can be ‘close enough’ and work fine.

While what you say is true, it’s not a recommendation in general that I’d support.

I consider it analogous to tires.Those that understand the differences between a 215x45/17 and a 225x40/17 can make the bump up (assuming a 7-1/2" rim) to improve aesthetics a bit and perhaps improve handling a wee bit. But the overwhelming majority of drivers probably have no clue what the difference is, like the ones who occasionally posts here wondering if a 235x45/20 will fit on their 17" rims. As a general recommendation it’s best for most to stick to the owner’s manual recommendation.

One can’t go wrong by following the manufacturer’s recommendations. One CAN go wrong by not doing so.

Well, when it’s just as easy to do something exactly as recommended as it is to deviate it would be silly to deviate. And the manufacturer’s recommendation is difficult to trump. But few here ever contradict the “book.”

We do on our own cars at home…

As an aside if I recall (CAN ANYONE TELL ME IF I AM WRONG), 5-30 can be a regular dino oil… However the 5-20 must be synthetic or semi-synthetic… This alone would have me staying with the 5-20… I just changed the oil in my wife’s Kia and it called for 5-20 so I ended up with semi-synthetic motorcraft as it was the least expencive.