Q: Brake light and oil weight on 2003 Toyota RAV4

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Approximately one month ago the brake light came on one evening when leaving work. I made an appointment the next day with a local garage. The next evening the brake light had went off. I kept the appointment and they checked the brake pads, rotor and calibers. Everything seemed to be fine. I had also checked the brake fluid and it was to the full line. Now yesterday evening the brake light was on again. This morning it had went off, but I noticed that it came back on after traveling approximately 5 miles. Their is not noticeably difference in driving the vehicle (i.e. throttling or braking). Nothing seems to be holding the vehicle back and when I touch the brakes the vehicle responds as usual. Any suggestions as to why the brake light keeps coming on.
Also one more question, I have been using 5W-30 oil in the vehicle as suggested by the manual. The vehicle has 85,000 miles on it. At some point and time should I change to a heavier weight - such as 10W-30?????
Thanks a bunch for your help.
(1) Answer
(1) Comments
Possible park brake 'on' reminder light intermittently coming on in the dash, make sure brake is fully set/seated in the off possition. Recheck mast cyl fluid level to be sure it is completely full. Possible fluid level 'sensor' issue. If NOT FULL have brake pad wear checked. No need to change oil viscosity!
Thanks for your reply. Lunch break at work and I just double checked the brake fluid level and it is on the maximum line. The front brake pads were replaced two years ago. I actually don't remember if I've replaced the back brake pads or not.