Would 10w40 be bad to put in my car between oil changes?

Actually with it being the summer you should be okay for inbetween oil changes. I can't tell you how many times gas stations usually do a switcharoo on you...putting 5w30 or 10w40 into 5w20 oil engine. the difference really is the thickness..its just a thicker oil.

5w20 can be hard to find, especially syntheic

You know Ken; it's amazing how big an issue this is. There are blogs and forums all over the Internet posting this question, and according to Barb Samardzich, vice president, powertrain engineering for Ford, this issue is poised to take on a life of its own.At the American Petroleum Institute (API) Automotive/Petroleum Industry Forum last month, she noted that Ford will be initiating a 10,000-mile oil change interval - that's more than 16,000 kilometres between motor oil changes.

if I were you I go to Walmart and buy 5w20 Synthetic Motorcraft for only $2.79 a quart last I checked, or go with 5w30 Valvoline MaxLife Synthetic for about $3.89. Valvoline MaxLife is a better choice since it has 1% of Zinc to greatly reduce friction of internal moving parts that in turn will give you better mileage MPG's (Slick50 contains 5% of Teflon PTFE which is not the best in the long run, it will eventually clog up all oil arteries in your engine). I have switched to Valvoline MaxLife and noticed a 1.5 mpg gain in my Saturn Vue. I have always used one quart "Marvel Mistery Oil" engine treatment in the engine and since January started using "Rich-Fuel"" US EPA Registered gas saver. It works very nicely I get a generous 20% better MPG's, much more power and so far its much better then anything I have ever used, you can find it @ www.rich-fuel.com , I wish you good luck with your Civic, cheers RoadRunner

it wont do anything. although most car makers recommend what grade oil to use whats more important is that you actually change your oil every 3000 miles or 3 months, whichever comes sooner. the grade of oil doesnt really have much of an affect on your engine, aslong as you get multiviscosity(which you did) and its not going into an old car that requires specific additives to prevent wear(which you dont)

If it was 10w-30 I would say it's OK but being 10w-40 I think thats a little too heavy a motor oil for a honda.

Don't worry, you'll be fine. Switch back on the next oil change for slightly better mileage.

It won't hurt anything at all, but the more of that type oil you add, the lower your gas mileage will be.

it should work ok. besides a heavier oil will be better in the summer.

dont use 10w40 in any thing that doesnt have taxicab in its name also please a qt of oil ?? short of cash/stay home

Its not going to do any damage it will be fine