dug06824 said:
is it ok to top off my car with 5w30 and if not what is everyone using in there cars , the dealer only has oil in bulk so i cant get it from them my car is about a week old today with about 630 miles, i took a 150 mile highway trip today and it looked like half a tank ,.sounds about right 300 per tank at 70 to 74 mostly
No, The car calls for 5w20, if the car has any problems and you are not running 5w20 non-synthetic oil, they can void the warranty on your motor. If you chose to run an oil differnt from 5w20 non-syn (as called for in the owners manual, and on the oil cap) thats up to you, but you need to drain the oil and replace all of it (including the 4qts of oil that STAYS in the oil coolers when you drain the oil pan. Thats right, when you drain the oil in your car, you only get half of it out, the other half stays in the oil lines and coolers.
Anyway, back to the topic, 2 things you NEVER do with oil :
NEVER mix oil weights, 5w20 with 5w30 or 20w50 with 10w30 or anything!
NEVER mix synthetic oil with non-synthetic oil.
5w20 can be a hard weight to find, only a few of the auto parts stores around me have it. I use the Castrol GTX 5w20 Non-Synthetic. Its the easyest to find, and its also a very good oil.
The Mazda dealer should have 5w20 oil in stock, since its what they SHOULD be using to change the oil in RX8s durring service. As you said they might only have it in bulk, but I know most Mazda dealers car Motorcraft oil in 1/4's....including 5w20 (Motorcraft is made by Ford who owns mazda, and its also a good brand of oil). If they dont have it in stock, ask the parts dept. to order it....cause they should be able to get it as the dealer can get anything the cars calls for in the owners manual (parts, fluid, bulbs, ect).
As far as fuel consumption, my car gets about 18-20 mpg in the city and about 22-24 on the highway. That ends up being around 240 miles to the tank city and 300 miles to the tank highway. The car has a 15.9 gal tank.
Something to remember, the 2nd bank of fuel injectors opens up at 3750RPM, thats about 74mph.....so if you cruise in 6th gear at about 72/73 MPH you can curise just below the point those injectors turn on. I have found I pickup 2mph if I cruise on the highway at 72mph vs 75mph.
Also the car gets the best fuel economy at 60mph in 6th gear, i know its slow, but you can't get any better MPG going faster or slower.
