The cap on my 2008 2.0L mazda 3 calls for 5w20. I have never owned a vehicle that has used oil that light before. Could I run something thicker like a 10w30? Or should I stick with what the manufacturer calls for. Also, I was wondering about running a full synthetic would that create a problem?

 

Most newer cars use a lower viscosity oil now a days..
I think it has something to do with higher efficiency/lower emissions?
I personally would stick with the manufacturers recommended oil weight

Also, most people say you shouldn't use full synthetic in a newer car until you reach a certain amount of miles. Not sure which is correct but I've heard anywhere from at least 5k miles up to 20k miles.

Its really up to you to do some research and find what you're comfortable with since it is your car. Oil is a tough subject matter with cars/engines and will always be debated.

 

This is the first "car" I have actually owned. I've driven nothing but trucks before this so the 5w20 caught me off guard. The motor I'm pulling out of it has 46xxx miles as well as the car. I bought a new motor that has 6k miles I Went ahead and got conventional 5w20 Valvoline. Hopefully this motor will last considerably longer then the previous one. But thanks for the advice.

 

Using a heavier weight or thicker oil is just going to make the engine work that much harder and will ultimately result in decreased fuel economy. Just stick with the 5w-20, or if you can't find that 5w-30.

As for whether to switch or not generally you should wait until after the engine does the bulk of it's break in. This usually happens between 500-5,000 miles. Once you're past that there's no problem running with full synthetic.

 

In a word, NO. Don't run thicker oil.
Tolerances between bearings and crankshafts/rods have gotten much tighter due to improved machining technology. As Spots indicated, increased drag, increased fuel usage, increased wear, due to a lack of lubrication on start-up.

I didn't switch to full synthetic until my '04 was at nearly 20k miles. I'm not saying that was right or wrong, just FYI. I also didn't see any major increases in fuel mileage until fairly recently and my car is approaching the 50k mark. Where I used to get 24-25mpg w/the AC on, I am now regularly getting 27-28mpg.
Take it for what it's worth. I have no definitive answers as to why either.

 

Heres the thing people dont really get about oil as far as how to read it.

(5w20) The first number indicates the oil viscosity at winter temp so it reads (5w=5 winter) and the second number indicates the oil viscosity at operating temp.

So if you pick something up like 10w30 no its not a bad thing since the oil is hot enough to pass easily the only thing with that example is that you might a little trouble getting the car started in the winter but it will start other than that its fine.

I myself has and still uses either 5w30 and 10w30 and i have noticed that not only did my car prefer full syn but it also liked the thicker oil.

 

Thanks for the advice. I live in south Texas so our winter time temperatures might hit 50 degrees. As far as synthetics go are there any preferred brands? Or are they all pretty much the same? Also how often should you change a synthetic?

 

My concern would be dry starting with the heavier oil. That's where most engine wear occurs anyway, so why make it harder for the engine to accomplish start-up lubrication?
If you live in a very hot climate my owners manual does recommend switching to 5w-30 for those months. I do live in a hot climate, as it can get up to 108*F here in the summer months (like recently), but since I only drive about +/-10k miles a year, and am using full synthetic I stay with 5w-20.

 

In that case, I would stick with a full synthetic and run 5w-30 all year. I run mine for 10k miles and change the filter after 5k.
Some argue that synths can be run up to 18k w/o a problem, and they may be right, I'm just not willing to take that chance... but I will say, that I had run the old Mobil1 in my Civic for up to 15k and did not experience anything bad. It came out relatively clean and no obvious sludge on the bottom of the pan.
I've been staying away from Mobil1 lately after using it for years. It has been said that in order to stay competitive in the market and maintain their profit they have switched to a cheaper synthetic base.
Depending how crazy you want to get, AmsOil, Royal Purple, Castrol or Valvoline all make excellent full synthetic oils, some harder to get and pricier. Others can be had at your local Wal-K-Mart.

 

Yeah, this summer has been brutal. I might go with royal purple down the line sometime. The shop that I work at has accounts with several suppliers which is helpful when parts are needed as I get them at cost