I rang up a local Ford dealer to ask them if it really is necessary to check/adjust the valve clearances on the zetec petrol engine and they said it was not imperative unless the engine had other problems. They also said they would charge about £130 to check. In the Ford service guide it says check/adjust every 100 000miles or 10 years whichever occurs first. In the Hayne's manual it says every 100 000miles but doesn't mention any time interval. What would you do ?