The book says recommended oil is 5-20. The dealer charges about $13 a quart for Mobil 1, but I can get 5-30 Mobil 1 at Costco for $30 for 6 quarts. Any opinions on the use of 5-30 instead of 5-20? This is for a 2005 Mazda3 5-door, not hard driving, in SF California area.

Thanks.

 

we just had a thread open up about the types of oil to use. you can do a search and you'll find it.

 

wasnt that my thread of when i first got my car then they were telling me all about oil... dont remember why though lol

 

As others have posted, check other threads for the oil weight debate. An interesting side subject is whether or not synthetic is worth it. Some data out there says - no, in fact it may be inferior. Again, there have been threads on this.

If the dealer cost is your big issue ($13 a quart does sound like a majorripoff), call around and see what an oil change place will charge. I know some oil change places will allow you to bring the oil of your choice in (and filter, if your also particular about that), and they'll do the change for a flat labor fee. Dealers very oftenare notthe bestdeal for getting a change done.

 

That's kinda' like taking your own food to a restaurant and asking them to cook and serve it to you.
I don't know that I'd be very comfortable doing that.

While I have lost some faith in Mobil1 lately, I still believe that synthetics are the way to go. I've got 9K miles on my current M1 5w-30 (and my second filter, BTW) and it's just starting to turn color. The finger test (not scientific) tells me that it's still protecting quite well, but within the next 1K I will be switching to Castrol Syntec 5w-30.
I ran M1 10w-30 in my Civic for over 80K, changing it only after 15K, and the car ran great.No oil burning, no frothy build up in the valve cover. The car ran on the same untouched short block for over 180K.#4 always had more leak-down than the others, a cracked/compromised ring I think, but that happened long before I converted it to M1. I wouldn't recommend that kind of mileage between oil changes anymore though. It probably wasn't the best idea even then!

 

A betteranalogy (IMO) would be to say its more liketaking your own bottle of wine to a restaurant, and asking them to serve it to you.

How much can they can screw up draining out old oil, and putting in the oil you brought? Probably this sounds offensive to hardcore DIYers, but if weather and/or age and/or lazyness mean you just don't feel like doing a self change, its an option.

 

https://www.mazdaforum.com/m_51917/tm.htm
this was from when i first bought my car hehehe. and say like the 3rd or 4th page shows what they have to say

 

The gist of it all is that I'm OK to go with the 5-30 so that's what I'll do.

BTW, I asked the dealer about bringing in my own oil and they said it's fine with them. I've been happy with their level of service for the past 2.5 years, other than the price of the M1. As for the analogy of bringing wine into a restaurant and asking them to serve it to you... reminds me of the time I went out to eat in Salt Lake City. But many places will let you bring your own wine; they charge a corkage fee.