I don't normally question the oil the Honda dealer puts in my 2020 CR-V, but new management recently took over and the bill for an oil & filter change today was $87 all in! I noticed they used synthetic oil (0W-20) but I don't think that would account for the big jump in price. In any case, I'm not concerned about the price, but this is the first time I noticed they were using such a low viscosity oil in my car. In fact, the service manager said 0W-20 is the only oil approved for my car... he pointed out that the filler cap specifies 0W-20, and I later verified the manual says the same thing without regard to local temperature range.

Honestly I never paid attention to this before but I'd like to understand why such a low viscosity oil is OK in Arizona where ambient temps top 115F in the Phoenix area, and rarely drop below 25F in the "colder" part of the state where I live. I searched for temperature-viscosity charts and the highest limit I found for 0W-20 was 30C (86F). I must be missing something...

 

charts found online can be really misleading unless they are specific to your engine/vehicle or include good source details. An air-cooled Porsche is going to be much more picky with viscosity relative to ambient temp than a late model CR-V.

-20 oil has been more or less default spec for 20 years for passenger vehicles. This is the more important number for engine operation and should depend less on ambient temps. Normal engine operating temps are above survivable ambient temps for humans. It will be really hard to expose the oil to ambient temps it can't handle and living to tell the tale. of course at that point the cooling system is on the hook for keeping the system happy.

The 0W is better for cold ambient temps and from what I've read recommended down to -40° generally.

further reading if you're interested

 

I've commented on this in the past on other forums. Most people don't seem to know what those two numbers ("xxw-yy) mean.

The first number is the weight of the oil, which is its viscosity - not how much a quart weighs. 5w oil is thinner, or lower viscosity, than 10w and so on.

The second number refers to additives in the oil which make it behave like a higher viscosity oil when it's hot. So 5w-20 oil has additives which increase its viscosity so that when hot it is the same as 20 weight oil.

I have no idea what viscosity a 0 weight oil would have. I assume that's just a convention to identify it as lower than 5 weight.

So your 0w-20 oil is very thin low viscosity when cold, which allows it to quickly flow into all the small ports and spaces and lubricate the engine. As the engine and oil warm up the viscosity increases and at full temperature you are in effect running a 20 weight oil.

I hope that clears things up for you. if your question is actually "Is the dealer screwing me?" there is a much simpler answer: Yes, most likely he is.

 

Thanks for replies! Very helpful. I was driving an '03 Oddy until I bought the CR-V in 2021 so this is my first exposure to synthetic oil. I have a couple of additional questions on this topic but first I'd like to review the material linked by hondamark35.

 

This is the "SAE viscosity grade" which corresponds to a measure of the dynamic viscosity under two test conditions at a specified temperature for each. in this example 0W is -35°C and -40°C.

Or for the layperson, how "thick" it will be relative to other grades when cold with smaller numbers being less "thick"

Additives are used to formulate multi-weight oil but the number is instead referring to the "SAE viscosity grade" which corresponds to a kinematic viscosity range at 100°C. in our example, SAE 20 is 6.9 to 9.3 cSt.

again for the layperson, this is the important number because this is what the oil is like for most of the time the engine is running- at normal temp. higher numbers tend to have more "cushion" between parts, but can't get in tight spots as well so there's a trade off. That's why the right number is important and the second number always match recommendation even if the first does not.

the viscosity decreases when it warms up, but less than it would with straight SAE 0W. that's why multi-weight is most often used.

 

"SAE J300" is going to be a helpful search term for you too.

 

I read the above-linked tutorial at the BITOG site... very helpful. If nothing else, I learned how much I don't know about today's oils! This all started when I read a FAQ on Honda's website that says all their engines 'are developed, tested & certified with petroleum based motor oils' but that synthetic oils may be used (https://engines.honda.com/company/faq). So I'm thinking, why do my car's specs call for 0W20 that isn't even available in a petroleum-based oil?! This discrepancy led to a 'debate' with the dealer's service manager. I had in my mind I was being charged extra for 'synthetic' oil, which the Honda FAQ clearly confirms isn't required. He insisted such a FAQ didn't exist (I should have saved the link on my phone). It didn't end well.

Now I learn on BITOG site that virtually all automotive oils today are either synthetic blends or fully synthetic. So I checked my previous oil change receipts and all used Honda part #08798-9045 (0W20), which turns out to be a synthetic blend. Apparently the term synthetic is thrown around a lot without qualification. This explains a lot of my confusion.

To further my confusion, a shop with an excellent rep was running a promo for 'synthetic' oil changes @ $65 and 'conventional' oil changes @ $35. That seemed to confirm what I suspected, so I ended up going there for a 'conventional' oil change -- the options were 5W20 or 5W30. I went with the 5W30 because I occasionally drive to Phoenix. There shouldn't be any issues running 5W-- (vs 0W-- as specified for my car) since I live in a hot climate, right? I paid just over $40 all in, so I figured I 'won'... But now, after reading in the BITOG tutorial that petroleum oils are a thing of the past, I checked the receipt and discovered the 'conventional' oil the shop used is actually a synthetic blend (Valvoline VV1770), not unlike what the dealer used, except with a different viscosity rating.

I realize now that my assumption about needing a higher '2nd number' was mis-informed... I should have opted for the 5W20. So my question now is whether 5W30 might harm my engine. Should I have it changed again for the 5W20?

 

I tend toward older vehicles with higher mileage so my logic is usually "enough of the wrong oil is better than the right oil running low" and I have plenty of anecdotal evidence that aligns with that. But I am also much less risk averse when it comes to vehicle maintenance than most. If I had a catastrophic failure on my daily driver I could still get to work the next day and probably have it fixed within a week or two. That scenario has happened in the past 6 months in fact!

my point- and to answer your question, the difference between the two grades is probably less important that the difference between clean, fresh oil going in and dirty, degraded oil coming out. It's very unlikely to do any damage with short term use, but long term stick with the 0W/5W20 for the best service life.