Its recommended you use a semi synthetic anyway so why use non recommended oils? most oils exceed the recommendations anyway, so you never have to buy an expensive one, its just not justified, your Landy wont thank you for it, the trick with oil is to change as often as you can then you get the best from it, battery's can be bought very cheaply from main stealer's Daf (the people who do trucks) have the exact same battery they use on Land Rovers, only difference is you done have the expensive logo on it, keep your receipt, put it in a plastic bag and when you change your battery, but the receipt in the plastic back and put it under the battery as your fitting it, then you wont lose it, and with felt tip put the date you bought it on the side of the battery, i always do that and seem to get another battery for free because it will go tits up before the 3 year warranty has finished