I use ramps for oil changes, I find it easier on the Elise/Exige then dealing with a jack and jack stands. Especially because of the limited and fragile jack points on the aluminum chassis.

Back up onto the ramps, being very careful not to drive off them. Leave the car in gear with the emergency brake on.

The aluminum panel under the engine must be removed to gain access to the oil pan and filter.

Remove the 11 x 8mm hex screws at the rear and sides of the panel. If you have a powered screw driver, now's the time to use it!

Then remove the 2 x M8 allen screws in the center. Some cars have a 13mm hex head bolt instead.

The panel will has no screws along the front side. It simply wedges in above a lip which eliminates the need for screws entirely. Simply pull backwards on the panel and slide it out of the way.

Place an oil drain pan under the car. I usually place mine on top of a 3-4" thick tool case to get the pan closer to the car and prevent spillage.

Remove the 14mm hex drain plug to drain the oil.

It's worth noting that the cars oil capacity is actually more then 4.5qts - Depending on year and options, the Elise and Exige have one or two oil coolers at the front of the car. Oil travels in the side sills of the car, through the coolers and back.

This oil stays in the car during a normal oil change service.

Drain the oil till it slows to a drip.

Re-install the oil drain plug and tighten to 27 ft-lb.

Use a new oil plug gasket to help reduce the chance of leaks. Though I've had no issues re-using the existing one.

Move the oil drain pan under the oil filter.

The oil filter is pretty strait forward. Using your favorite oil filter wrench (strap or cap-style), just spin it counter-clockwise. Oil will come spilling out of the sides. I usually spin it quickly, then stop as soon as it starts puking down the sides.

Let it slow down to a drip and spin it off the rest of the way.

I pre-fill the new oil filter with clean oil to potentially reduce the amount of oil the engine has to pump back in on the first startup. The Mobil 209 filter I use easily soaks up half a quart.

This may be totally unnecessary, but it gives me peace of mind.

Wipe some fresh oil onto the new oil filter's gasket. This helps get a proper seal when re-installing.

For what it's worth, here's a size comparison between the stock Lotus oil filter and the much larger Mobil M1-209

Inspect the oil filter adapter.

I always visually inspect the oil filter mounting surface, and clean it with a clean paper towel. You don't want anything like dirt or the gasket from the old filter preventing a good seal. (you only make that mistake once)

Screw on the new oil filter.

The side of my Mobile filter says hand tight + 3/4 turn. So I tighten it till I cant spin it anymore, then use my strap wrench to go the rest of the way.

It's worth checking again now, before you fill up the oil.

Remove the oil fill cap.

It screws off by hand but is always mysteriously tighter then when you put it on last time.

Using a small funnel, pour in the remainder of the 4.5 quarts.

Remember you used approximately .5 to fill up the filter.

Re-install the oil cap.

At this point I jump in and start up the car. I like to do this before I put the belly pan back on because it's hard to check for leaks otherwise. Run the car for a 30 seconds or so just to get the oil moving around.

Turn of the car and inspect the drain plug and filter for any signs of a leak.

Now check the dipstick to make sure the level is where you want it.

I always check mine on the ramps, so I expect the dipstick to read a little high with the oil tilted toward the front of the car. Mine is usually near the top of the two marks at this point.

Your pretty much done, time to slide in the panel and tighten down the bolts.

I usually slide under the car, holding the panel on top of me. Push the front of the panel up into the groove it sits in (take care getting both sides in).

Then I install the 2 large center screws, not tightening them all the way. Just enough to hold the panel in place but still slide around a tad to keep the surrounding screws from binding.

Install the rest of the screws, and tighten everything down.