Most minor, single mouth ulcers are caused by damage to the mouth, for example by accidentally biting the inside of your cheek while eating, or from a sharp tooth, food or filling.
I have a 2005 Honda Element. The owners manual states the brake fluid should be replaced every 3 years. When I asked the dealer to replace the brake fluid, they said it was going to cost $190. I told them last time they did it, it was only $27.
1 Also look for instructions on how frequently to change your transmission fluid. 2  While you can add fluid when it gets low, many car manufacturers recommend a transmission fluid change every 30,000 to 100,000 miles (48,000 to 161,000 km), depending your car.