0w20 would actually be the wrong viscosity, in your case
Why not stick with 5w20 fully synthetic mobil 1 . . . ?
@galant
For warranty purposes I would stick with 5W20 which should be fine year around. I prefer 0W30 in the winter but I never have to worry about warranties in my old cars.
Based on what I have read online, even thought both 5W-20 and 0W-20 are full synthetic, the “0” is a higher grade synthetic based on the European classification of oils.
I am in CA desert, so cold in here is around 30 which is summer based on what I am used from New England.
^What car in particular?
My honest opinion (since you asked for one) is that 20 weight oils are largely a CAFE fiddle; they might not do any harm, but they don’t provide “added value” beyond the 0.4% or so fuel economy increase over a 0w30/5w30.
If you look at cars sold both in the US and in the EU (not subject to CAFE laws), they almost NEVER spec a XXw-20 wt oil in europe! If they had some intrinsic value beyond CAFE, you’d expect to see 'em called for everywhere…
If I were you, I’d run what the factory calls for until the warranty expires, then go to a quality 5w30 and never look back. If you lived somewhere that had winters, I’d be open to running a 0w30…but where you live, that’s just a somewhat more fragile oil (more VIIs) for no real benefit.
0w-20 would give you better cold weather starting then mineral 5w20 but it would be worth while checking with the manufacturer. Even prior to mandatory use in some cars today, car motors of old using synthetics for hard use were more economical to maintain over time in the police cars we used. The problem is, if a car is not certified to run on a particular motor oil type, you don’t want to chance voiding any warranty left if the viscosity is technically different. That’s not a problem for fleet cars driven routinely to high mileages, but it is for the average new car buyer.
Even if I were totally convinced that synthetic 0w -30 weight was better then 5w30 mineral at shorter intervals, or 0w20 was better then 5 w20, mineral or synthetic I would not use it until the warranty had run out…by a significant margin. The reason is, many car makers will still honor warranty repair, even with some grace period after it expires.
@grovej: I would also recommend Amsoil. Where I live it can be had for about $6/qt, and between it and Valvoline synthetic, when I use those oils my engine doesn’t use a drop between changes. It also seems the oil pressure is very consistent between the first day and right before I change it, which seems to indicate that it isn’t thickening or degrading.
Mobil1 is good oil, but my cars always seem to use a bit of oil with Mobil1 on board.
If a car calls for 5W20 and you use 0W20, I cannot see this causing any issues. In fact it could be a good thing if you live in Minnesota during the winter. The oil will be thinner when cold but should have the same operating temp once hot. I understand that in order to attain protection with this think of an oil, they have to use some very high quality base oils so they may do a better job of protecting the engine. Now if a warranty issue with the engine were to come up, car makers are notorious for trying to get out of coverage if they see anything you might have done wrong. That being said, it is a gamble if you want to use something different or not. I don’t know what kind of car it is but does it typically have warranty claims with the engine? If not, I would probably do this. I am guessing Toyota but don’t know.
I personally run Mobil 1 0W40 European in my vehicles which call of 5W30. They start an run great cold as well as hot. I have been told by many that this behaves as a very think 40W when warm so it shouldn’t be an issue. I understand it also has a very high quality base oil compared to other M1 products of the same price so that is my main reason for using it. I did notice that my oil got dirty really quick after changing oil on the first change with this. My second Geo Metro’s oil turned black within 1000 miles so I changed it at that point. My feeling was that the previous owner didn’t change the oil on time but it seems fine now. Yes, I am running oil rated for use in a Mercedes Benz AMG in a Geo Metro! Go ahead and laugh. Another funny point is that this car uses the same oil filter as my riding mower
@cwatkin
He lives in southern California
No harsh winters
@cwatkin
Oh, I am completely with you as far as using synthetic 0w20 when car calls for 5w20, synthetic or otherwise, IMHO, 0w20 synthetic would be an excellent alternative. But, if the car is still under warranty and the manual says nothing about it being an option, check with the factory or don’t use anything else till the warranty runs out. It just makes sense to me. You are running older out of warranty cars ? Go for it !
But, before anyone goes with expensive optional synthetics and plans to change them at the regular 5k interval, remember this. If you live in rust belt where cars traditionally rust through in about 15 years and you put fewer then 15k miles per year on your car, what good are you doing. Regular mineral oil can make modern motors last 200k miles. You may need other reasons, like cold weather starting, an environment concern or longer intervals with less expense to make it worthwhile.
I went to a bike swap meet with my mechanic friend today and we talked about my change to full synthetic . . he made the same suggestion as you cwatkin, change the oil after 3000 since the full synthetic basically “washes” the internals. I only had 27,000 on this Toyota 4-cylinder beforehand, still think that it’s necessary? I’m gonna take a look at the oil on the dipstick today and see if it looks “dirty”. I changed the oil during the first 27,000 every 3000 with a filter each time, and I’m mostly highway driving. My mpg went up from 43 to 47 mpg highway (Toyota Yaris 1.5) after the synthetic change. Still think that a change at 3000 is necessary? Rocketman
BTW, no leaks or drips whatsoever. Rocketman
3000 is unnecessary with mineral oil. Synthetic oil changes at 3000 miles eliminates the advantages for even having a economy car that small. Maybe the first at 5k and subsequent ones at 7500 would make sense. Oil change fetish is alive and well. 
Check your oil at 500 miles. Does it look really dark? Check it again at 1000 miles. If very dark, then change it then. Otherwise keep running it and see how it looks each 500 mile increment. If it is really dark at 3000, then change it. Otherwise run to a normal OCI.
I have been running 5k changes since the initial change that turned dark pretty quick which may be overkill. I had to remove the valve cover in both my Metros to replace the gasket. The first one was clean inside. The second one was nasty with visible sludge that I could scrape up. I did a 1000 mile oil change right off the bat on this one as the oil was dirtier than my normal 5k changes. Obviously this one had been neglected before I owned it and I want to make sure that sludge is being removed by an oil change. I also don’t want to flush it out. I have heard lots of horror stories about using quick flushes such as adding Seafoam to dissolve this all at once. Large chunks break loose, passages get clogged and parts become starved of oil, doing severe damage. If the engine runs ok with this sludge, it seems best to slowly take care of this by changing the oil with a quality grade that gradually dissolves into the oil where it is removed by the filter and during changing.
Checked the oil at ~1800 miles and it seems relatively clean. The engine has only 45K miles on it and the previous 15K miles used Motorcraft Semisynthetic, so maybe not that dirty.
I was at Wally world again and the house brand synthetic at ~$17 per gallon is very tempting. Any follow up word on who makes the oil for WM?
Warren and Coastal are the two common ones that make the store brands. That being said, look at the certifications. European specs ACEA are considered more stringent than API specs. Look for Mercedes, Audi, Porsche, etc. that many of the better oils meet. If it doesn’t meet these, also consider specs required by US makers such as GM Dexos. This is also a good spec to look for. It may not be quite what the Euro ones are but it is still very good. I am not familiar with all the specs but each maker has one for their higher end cars. Chrysler has one, Ford has one, and so on. They don’t put conventional oil in a Viper for example.
Between the low miles, use of a semi-synthetic, and the highway miles, I suspect you have a pretty clean engine. I would just run with it and not worry. MY examples were higher mileage at the switch and/or had been neglected by previous owners. I also have a friend who is a big Mustang enthusiast and he runs the Ford semi-synthetic like you.
Also, something else to consider is that lots of meeting spec is simply paying a licensing fee to the company or agency. Remember that there may be a good oil inside of a generic looking bottle going for a good price because it isn’t paying to be advertised or expensive licensing fees. I personally don’t think the Wal-Mart oil is bad. I once dated a girl who went 10,000 miles without even looking at her oil on the standard blend. It was a Ford Focus and I changed the oil. Besides the oil looking extremely dirty and being a quart low, the inside of the valve cover looked perfectly clean. This oil was obviously still doing its job at this time although I think she was pushing it. Most of her miles were highway so I am sure that helped.
Just make sure the store brand meets or exceeds the specs required by your engine. Most should these days except for some no-names I see at convenience stores. Some of that stuff is only suitable for chainsaw bar oil in my opinion. While I know Wal-Mart does sometimes spec lower quality goods, I suspect that their automotive dept. is a big enough money maker that they don’t want to NOT to be able to change oil in certain makes of cars. The oil seems to meet all mainstream specs from what I can tell.
I believe that I’m going to check my oil level and color every 500 miles and change at 6000. My mechanic friend told me that variable valve timed engines are sensitive to dirty oil, but I believe that oil filters filter out almost anything to micron sizes. If I’m worried about it and the oil looks dirty at 3000 I’ll either do a complete oil & filter or change the filter and top it off. I’m kind of agreeing with dagosa here and believe that my approach might be overkill, given the kind of driving that I do. Car maintenance IS a fetish and we obsess, but so what? My little Yaris is quite reliable, comfortable, quick, and returns mpgs in the mid 40s all the time. I drive 99% of the time by myself, so the choice for me was logical. I’m enjoying this conversation and have learned a lot about the whole synthetic vs. mineral debate. Thanks to everyone for your comments! Rocketman
Galant . . . that was my original post. Is Wal-Mart @ $17 for 5 quarts as good as Pennziol or Mobil 1 @ $25 for 5 quarts? I went to Pennsoil @ $22 for 5 quarts with an on-line rebate from Pennzoil for $10 (bringing the price down to $12 for 5 quarts or $2.40 a quart!). I’ve now found on-line rebates for both Pennziol and Mobil 1 so I believe that I’ll do this dance from here forward and get my synthetic oil for $2.40 or so a quart. Happy motoring! Rocketman
@rocketman For mostly highway driving, 3000 mile intervals are too frequent with today’s oils. Even mineral non-synthetic oils. Highway driving is very easy on an engine. Toyota now has gone to 10,000 mile intervals with synthetic oils, but I think that’s going too far!
I would go 5000 miles, as Toyota recommended up till last year for oil and filter change. If you do all the other maintenance, the engine may very well outlast you!